5*5  0 
4- 


L.  \ 


L I  E>  RAHY 

OF   THL 

UNIVERSITY 

OF    ILLINOIS 


NATURAL  HISTORY  SURVE 


;. 


550.5 
FI 

v.fc,cop.2. 


.--.• 


Return  this  book  on  or  before  the 
Latest  Date  stamped  below. 

Theft,  mutilation,  and  underlining  of  books 
are  reasons  for  disciplinary  action  and  may 
result  in  dismissal  from  the  University. 
University  of  Illinois  Library 


JUN 


L161—  O-1096 


Field  Columbian  Museum. 

Publication   123. 

Geological  Series.  Vol.  II,   No.   10. 


NEW  CRINOIDS  FROM  THE 
CHICAGO  AREA. 


BY 


Arthur  Ware  Slocom, 

Assistant  Curator,  Section  of  Invertebrate  Paleontology. 


Oliver  Cummings  Farrington, 
Curator,  Department  of  Geology. 


Chicago,  U.  S.  A. 

October  31,   1907. 

Issued  Jan.  3  1908 


NEW   CRINOIDS   FROM   THE   CHICAGO   AREA. 


BY  ARTHUR  WARE  SLOCOM 


In  the  fall  of  1905  the  attention  of  the  writer  was  called  to  the  fact 
that  fossils  were  being  found  at  a  quarry  operated  by  the  Illinois  Steel 
Company  for  limestone  for  flux,  at  Romeo,  Illinois.  Upon  visiting  the 
quarry  it  was  found  that  not  only  was  the  limestone  itself  fossilf erous, 
but  that  silicified  fossils  were  abundant  near  the  bottom  of  large 
clay  pockets  which  were  exposed  at  various  places  in  the  quarry. 
These  clay  pockets  occupy  large,  irregular  shaped  cavities  in  the  lime- 
stone. The  larger  ones  are  1 5  or  more  feet  deep  and  their  width  is 
often  greater  than  their  depth.  In  some  instances  several  are  connected, 
their  connections  following  the  jointing  of  the  limestone.  These 
cavities,  or  "pot-holes"  as  they  are  sometimes  called,  often  associated 
with  furrows,  are  to  be  seen  in  many  places  along  the  Chicago  Drainage 
Canal  where  the  surface  of  the  rock  is  exposed.  The  cavities  vary  in 
size  from  a  fraction  of  an  inch  in  depth  to  those  mentioned  above. 
These  cavities  or  pot-holes  must  have  been  in  part  subjected  to  the 
action  of  running  water  since  their  sides  are  smooth.  They  are  fre- 
quently broader  at  the  base  than  above  and  may  even  be  cone-shaped, 
with  the  apex  of  the  cone  above.  Their  filling  is  for  the  most  part 
a  blue  homogeneous  clay.  This  contains  small  silicified  fossils  of  Niag- 
aran  age,  small,  modern,  fresh-water  shells  and  fragments  of  pyritized 
and  charred  wood.  No  large  boulders  or  pebbles  occur  in  the  clay, 
although  these  frequently  form  a  capping  of  the  pockets.  The  question 
of  the  origin  of  the  filling  of  the  pockets  is  a  matter  of  no  little  interest. 
The  clay  could  not  be  of  preglacial  origin  because  of  its  content  of 
wood  and  modern  shells.  If  of  postglacial  origin,  the  presence  of 
the  Niagaran  fossils  is  difficult  to  account  for.  A  wall  of  the  quarry 
showing  typical  pockets  is  represented  in  Plate  LXXXII.  A  single 
one  in  more  detail  is  represented  in  Plate  LXXXIII. 

During  the  fall  of  1905  and  the  spring  and  summer  of  the  following 
year,  over  400  fossils  representing  38  species  were  collected  by  the 
writer  from  these  clay  pockets.     These  fossils  were  divided  as  follows: 

Corals 293  specimens,    1 5  species ; 

Sponges , .    20  specimens,      3  species; 

Bryozoans 12  specimens,      4. species; 

273 


274  Field  Columbian  Museum  —  Geology,  Vol.  II. 

Crinoids 21  specimens,      7  species; 

Brachiopods 96  specimens,      9  species; 

Trilobite 1  fragment. 

Of  this  material  the  corals,  sponges  and  crinoids  showed  a  great  simi- 
larity to  those  found  at  St.  Paul,  Indiana,  and  Perry  county,  Tennessee, 
and  a  number  of  species  described  from  those  localities  were  recognized. 
It  was  found  that  the  manner  of  preservation  of  the  clay  pocket  fossils 
differed  from  that  usual  to  those  of  the  limestones  of  the  Chicago 
Area  in  that  the  latter  are  natural  casts  and  molds  .while  the  clay-pocket 
fossils  are  silicified.  Search  in  the  surrounding  limestone  at  Romeo 
failed  to  show  similarly  preserved  fossils  in  place  there  and  only  a  few  of 
the  clay-pocket  species  were  discovered.  The  spoil  heaps  of  the  Chicago 
Drainage  Canal  were  then  studied  and  near  Lemont,  Illinois,  the  species 
found  in  the  clay  began  to  appear,  until  all  the  brachiopods  and  part 
of  the  corals  were  found.  Many  of  these  were  in  a  similar  state  of 
preservation  to  those  of  the  clay  pockets.  Of  the  seven  species  of 
crinoids  occurring  in  the  clay  three  were  found  in  the  Lemont  limestone 
and  three  more  were  represented  by  species  of  the  same  genera.  Over 
400  fossils,  representing  76  species,  were  collected  at  this  locality, 
divided  as  follows : 

Sponges 3  specimens,     1  species ; 

Corals 40  specimens,     6  species ; 

Cystoids *. 62  specimens,     6  species; 

Crinoids 149  specimens,  32  species; 

Bryozoans 10  specimens,     6  species; 

Brachiopods 62    specimens,   11   species; 

Mulluscs 9  specimens,     5  species; 

Trilobites 82  specimens,     9  species; 

The  finding  of  these  silicified  corals  and  brachiopods  at  Lemont 
identical  with  those  occurring  in  the  clay  pockets,  left  little  room  for 
doubt  that  the  clay  and  fossils  found  in  it  were  residual  from  the 
Niagaran  limestone,  and  that  they  had  been  transported  to  Romeo  from 
the  Lemont  Area.  The  Romeo  quarry  is  distant  about  five  miles  in  a 
southwesterly  direction  from  the  point  near  Lemont  where  the  cor- 
responding fossils  were  found.  Both  localities  are  in  the  valley  known 
as  the  Chicago  Outlet,  through  which  the  waters  which  occupied  the 
basin  of  Lake  Michigan  at  the  close  of  the  glacial  period  discharged 
into  the  Mississippi  River.  The  flow  of  these  waters  would  have  been 
sufficient  to  transport  material  like  that  described  from  Lemont  to 
Romeo,  although  the  period  and  exact  circumstances  of  this  deposition 
have  not  as  yet  been  determined.  The  silt-like  nature  of  the  deposit 
in  the  clay  pockets  shows  that  it  occurred  in  quiet  waters. 


Oct.,  1907.  New  Crinoids —  Slocom.  275 

Among  the  crinoids  collected  in  this  work  several  proved  to  be 
either  hitherto  undescribed  or  new  to  the  Area.  Of  these  five  had  been 
described  from  other  localities  and  nine  were  new  species.  Of  three  spe- 
cies previously  described  by  other  authors,  additional  characters,  which 
are  here  given,  were  obtained  from  specimens  found  by  the  writer. 
The  nine  new  species  are  here  described  and  five  species  previously 
described  from  other  localities  are  here  re-described.  A  total  of  seven- 
teen species  of  crinoids  is  therefore  described  in  the  present  paper. 


CLASSIFICATION  AND  TERMINOLOGY 

The  classification  here  used  is  that  prepared  by  Wachsmuth  and 
Springer  and  is  substantially  that  given  in  the  English  edition  of 
Zittel's  Text-book  of  Paleontology.  The  terminology  of  Wachsmuth 
and  Springer  is  also  adhered  to.     It  may  be  briefly  stated  as  follows: 

Crinoid:  A  normal  crinoid  consists  of  a  crown  attached  by  its 
dorsal  extremity  or  base  to  a  stem  or  column  which  is  fixed  to  some 
solid  body  by  a  root. 

Crown:  All  of  the  crinoid  above  the  stem.  It  includes  the  calyx 
and  the  arms. 

Calyx:  The  body  of  the  crinoid  without  the  free  arms  or  stem. 
It  incudes  the  dorsal  cup  and  ventral  disc  or  tegmen,  and  within  it  are 
enclosed  the  more  important  organs  of  the  body. 

Dorsal  Cup:  That  part  of  the  calyx  below  the  point  of  attachment 
of  the  free  arms.  It  is  usually  more  or  less  cup-shaped  and  is  composed 
of  two  or  more  rows  of  plates  having  a  more  or  less  complete  pentamer- 
ous  symmetry. 

Ventral  Disc,  Tegmen,  Dome,  etc.:  That  part  of'the  calyx  above  the 
point  of  attachment  of  the  free  arms.  It  is  made  up  of  plates  more  or 
less  regularly  arranged  and  contains  the  mouth  and  usually  the  anal 
opening. 

Base:  That  part  of  the  dorsal  cup  lying  between  the  radial  plates 
and  the  stem.  It  consists  of  a  single  row  of  plates,  the  basals,  in  a 
monocyclic  base,  and  of  two  rows  of  plates,  the  basals  and  infrabasals, 
in  a  dicyclic  base. 

Rays  or  Brachials :  The  series  of  plates  which  rests  upon  the  basals 
and  extends  up  to  and  forms  the  arms.  The  first  plate  of  the  series 
is  always  a  part  of  the  dorsal  cup,  the  others  may  or  may  not  be  a  part 
of  the  cup.  There  are  five  of  these  rays,  except  in  the  Zophocrinidae, 
and  they  are  designated  as  follows:  (Figs.  1  and  2)  (1)  right  posterior 
ray,  (2)  right  anterior  ray,  (3)  anterior  ray,  (4)  left  anterior  ray,  and  (5) 
left  posterior  ray. 


276 


Field  Columbian  Museum  —  Geology,  Vol.  II. 


Interbrachial  areas  (I  Br.*):  The  plates  in  camerate  crinoids  sit- 
uated between  the  rays. 

Anal  or  posterior  interradius  (X.  a.  a.) :  The  area  situated  between 
the  right  and  left  posterior  rays  and  leading  up  to  the  anal  opening. 

Basals  (B) :  The  circle  of  plates  directly  below  the  radials  and  alter- 
nating with  them.     In  a  monocyclic  base  they  join  the  column. 

Infrabasals  (I  B) :  The  first  row  of  plates  in  a  dicyclic  base.  They 
separate  the  basals  from  the  column  and  are  radial  in  position. 


^9^ 


'^m 


Fig.  2.    Diagram  of  a 
Dicyclic  Crinoid. 


Fig.  1.    Diagram  of  a  Monocyclic,  Camerate  Crinoid. 


Radials  (R) :  The  first  plate  of  each  ray,  usually  resting  on  the  ba- 
sals. In  some  families  part  of  the  radials  are  divided  horizontally.  The 
parts  of  these  plates  are  called  superradials  (Rs)  and  inferradials  (Ri), 
respectively. 

Costals  (C) :  Those  plates  of  each  ray  extending  from  the  radials,  on 
which  they  rest,  up  to  the  first  bifurcation. 

Distichals  (D) :  All  plates  of  each  ray  between  the  first  and  second, 
bifurcation. 

Palmers  (P) :  All  plates  of  each  ray  between  the  second  and  third 
bifurcation.  Any  plates  of  a  higher  order  than  these  are  called  post- 
palmers. 

*  The  letters  in  parenthesis  refer  to  those  of  Figs.  1  and  2. 


Oct.,  1907.  New  Cricoids  —  Slocom.  277 

Inter distichals  (I  D) :  Any  plates  situated  between  the  distichals. 

Anal  Plate  (X) :  First  plate  of  the  anal  interradius.  It  often  rests 
upon  the  posterior  basal    and    is  in  line  with  radials  or  nearly  so. 

Interbrachials  or  interradials  (I  Br) :  Any  plates  of  the  interbrachial 
areas. 

Radianal  (RA) :  A  plate  resting  within  the  angle  formed  by  two 
basals  and  below  the  right  posterior  radial  plate.  It  joins  the  anal 
plate  on  the  left  and  occupies  the  position  of  an  inferradial. 

Distal:  Farthest  from  the  stem. 

Proximal:  Nearest  to  the  stem. 

Lateral:  Pertaining  to  the  side. 
Authors  differ  widely  in  the  use  of  the  terms" mold,"  "cast"  and  "im- 
pression," but  as  used  in  this  paper  they  may  be  defined  as  follows: 

Natural  mold:  A  matrix  or  cavity  in  the  rock,  formed,  by  natural 
causes,  around  an  organism  when  the  rock  was  plastic.  The  external 
form   of   the   organism   is   thus   preserved. 

Natural  cast :  The  rock  filling  of  the  internal  or  visceral  cavity  of 
an  organism,  the  shell  of  the  organism  having  served  as  a  mold.  In 
many  cases  (see  Plate  LXXXIV,  Figs,  3  and  10)  the  shell  is  afterwards 
dissolved  out,  leaving  the  mold  and  cast  in  position.  In  such  cases  the 
space  between  the  two  indicates  the  thickness  of  the  shell. 

Impression:  An  artificial  cast,  made  in  a  natural  mold,  which  shows 
the   external   features   of  the   organism. 

In  the  following  descriptions  three  materials  are  referred  to  as  being 
used  for  making  impressions,  viz. :  plaster,  roller  composition,  referred 
to  as  "composition,"  and  vulcanized  rubber,  referred  to  as  "rubber." 
The  methods  of  making  impressions  from  the  two  latter  substances 
have  been  previously  described  by  the  writer.*  In  addition  to  the 
details  there  given  it  may  be  remarked  that  in  many  cases  the  shape 
and  position  of  the  mold  in  the  rock  is  such  that  it  is  difficult  to  keep  the 
rubber  in  place  while  vulcanizing.  In  such  cases  it  is  necessary  to  build 
a  retaining  wall  of  plaster,  or  to  cement  a  metal  ring  around  the  open- 
ing of  the  mold ;  this  prevents  the  rubber  from  spreading  when  the 
pressure  is  applied  with  the  clamp,  and  a  perfect  impression  is  assured. 

*  Science,  1907,  X.  S.  Vol.  XXV,  p.  591. 


278 


Field  Columbian  Museum  —  Geology,  Vol.  II. 


DESCRIPTION  OF  GENERA  AND  SPECIES. 

Order    I.     LARVIFORMIA. 

Family  PISOCRINID^. 

PISOCRINUS  De  Konik. 

No  members  of  this  genus  have  hitherto  been  reported  from  this 
Area.  Representatives  of  three  species,  P.  benedicti,  P.  gemmiformis 
and  P.  qainquelobus  were  found  by  the  writer.     The  generic  characters 

are  as  follows:   Calvx  small, 
ill 


Fig.  3.    Diagram  of  Pisocrinus.    (After  Bather). 


globular,  subconical  or  sub- 
cylindrical.  Facets  for  the 
attachment  of  the  arms  wide, 
angular  and  projecting  limbs 
of  the  radials  short. 

Basals  five,  forming  a  tri- 
angle. The  three  plates  sit- 
uated at  the  angles  larger 
than  the  other  two.  Radials 
five,  extremely  irregular,  only  the  left  posterior  and  anterior  radials 
in  contact  with  the  basals.  These  are  more  than  twice  the  size  of  the 
other  radials.  The  left  anterior  radial  is  angular  below,  resting  on  the 
lateral  edges  of  the  two  large  radials.  The  right  posterior  and  right 
anterior  radials  rest  upon  a  large  inferradial  which  separates  them  from 
the  basal  plates.  Notwithstanding  the  great  difference  in  size  of  the 
radials,  their  distal  edges  are  about  equal.  Anal  plate  rests  on  the 
processes  of  the  posterior  radials. 

Arms  neither  branched  nor  pinnulate. 


Pisocrinus  gemmiformis     S.  A.  Miller,  Plate  LXXXIV,  Figs.  1-4. 
1879.  P.  gemmiformis      S.   A.  M.,  Jour..  Cincin.  Soc.  Nat.  Hist. 

Vol.  2,  p.  113,  PI.  9,  Figs.  6  a-c,  Osgood,  Ind. 
1886.  P.  gemmiformis      Wachsmuth  &   Springer,   Rev.   Palaeocr. 

Pt.  Ill,  p.  184. 
1892.  P.  gemmiformis      S.  A.   M.,   17th  Rept.   Geol.   Surv.    Ind. 

p.  636,  PI.  VI,  Figs.  10-12,  Madison,  Ind. 
Calyx  globular,  depressed  at  the  base:    plates  thick,  sutures  in- 
distinct, surface  smooth  or  finely  granular. 

Basal  plates  five,  forming  a  nearly  equilateral  triangle  and  curving 


Oct.,  1907.  New  Crinoids  —  Slocom.  279 

into  the  basal  cavity.  The  three  plates  at  the  angles  are  larger  than 
the  other  two.  The  basal  triangle  is  followed  by  three  large  plates 
which  comprise  the  principal  part  of  the  calyx.  These  are  the  an- 
terior and  left  posterior  radials  and  an  inferradial  plate.  The  left 
posterior  radial  rests  upon  two  basals,  the  other  two  plates  rest  upon 
three.  The  other  three  radials  are  small,  angular  below  and  are  not 
in  contact  with  the  basals;  the  left  anterior  radial  rests  upon  the 
sloping  sides  of  the  adjoining  radials,  and  the  right  posterior  and 
right  anterior  radials  each  rest,  one  side  upon  the  inferradial  and  one 
side  upon  the  adjoining  radial.  The  distal  edges  of  the  radials  are 
provided  with  short  processes  at  their  juncture  with  the  lateral  edges 
which  form  a  wide,  shallow,  angular  excavation  for  the  attachment 
of  the  arms. 

Arms  not  preserved. 

Owing  to  the  thickness  of  the  plates,  the  natural  casts  of  this  genus 
bear  little  resemblance  to  the  exterior  of  the  calyces.  The  natural  casts 
of  this  species  are  in  the  form  of  a  triangular  pyramid ,  truncated  by  a 
cylinder.  The  base  of  the  pyramid  is  nearly  flat  and  is  formed  by  the 
inner  surfaces  of  the  basal  plates.  One  face  of  the  pyramid  is  formed 
by  the  inferradial  plate  and  the  other  two  by  the  lower  part  of  the 
large  radials.  The  cylinder  is  formed  by  the  three  small  radials  together 
with  the  upper  part  of  the  two  larger  ones. 

The  distinguishing  characteristics  of  the  exterior  of  the  calyx  of 
this  species  are  its  globular  form,  with  its  depressed  base,  gradually 
curving  into  the  facet  for  the  attachment  of  the  stem.  The  casts  are 
distinguished  by  the  triangular  pyramid  at  its  base. 

Locality:  This  species  is  comparatively  abundant  in  the  clay 
pockets  in  the  limestone  at  Romeo,  Illinois,  where  it  occurs  as  silici- 
fied  specimens  which  appear  to  be  identical  with  those  of  the  type 
locality.  In  the  spoil  heaps  along  the  Chicago  Drainage  Canal  near 
Lemont,  Illinois,  it  is  one  of  the  most  abundant  crinoids  in  the  form  of 
natural  molds  and  casts,  and  a  single  silicified  specimen  was  found 
there. 

Pisocrinus  benedicti     S.  A.  Miller,  Plate  LXXXIV,  Figures  8-1 1. 

1892.  P.  benedicti  S.  A.  M.,  17th  Rept.  Geol.  Surv.  Ind.,  p.  639, 
PI.  VI,  Figs.  3-16. 

Calyx  deeply  cup-shaped,  moderately  expanding  to  the  upper 
third,  rounded  at  the  base  and  slightly  constricted  at  the  top;  plates 
thick,  surface  smooth  or  finely  granular. 

The  plates  of  the  calyx  are  the  same  in  number  and  position  as 
in  P.  gemmijormis,  but  the  basals  are  larger  than  in  that  species,  so  as 


280  Field  Columbian  Museum  — [Geology,YVol.  II. 

to  be  visible  in  a  side  view  of  the  calyx,  and  the  two  large  radials  and 
the  inferradials  are  longer  in  proportion  to  their  width,  making  the 
calyx  higher  than  wide.  The  rounder  base  is  provided  with  a  deep 
basal  cavity  whose  sides  are  subparallel. 

The  natural  casts  are  subcylindrical,  moderately  expanding  to  the 
arm  bases.  The  base  is  flat,  having  three  slight  protuberances  which 
give  it  a  subtriangular  appearance  from  below. 

The  specimens  here  described  appear  to  be  more  cup-shaped  than 
Miller's  original  figures  indicate,  and  no  mention  is  made  by  him  of  the 
abrupt  margin  of  the  basal  cavity.  Examination  of  several  hundred 
specimens  of  this  species,  from  the  type  locality,  shows  these  features 
to  be  characteristic  and  those  which  most  easily  distinguish  this 
species  from  P.  gemmiformis. 

Locality:  The  specimens  (Mus.  No.  P  8481),  consisting  of  natural 
molds  and  casts  on  which  the  above  description  is  based,  were  collected 
by  the  writer  in  the  spoil  heaps  of  the  Chicago  Drainage  Canal  near 
Lemont,  Illinois.  A  single  incomplete  individual  from  the  clay  pockets 
at  Romeo,  Illinois,  is  doubtfully  referred  to  this  species. 

Pisocrinus  quinquelobus  Bather,  Plate  LXXXIV,  Figures  5-7. 
1893.  P.  quinquelobus  Bather,  Crinoidea  of  Gotland,  Part  I,  p.  27. 

1895.  P-  milligani  Miller  &  Gurley,  Bull.  7  Ills.  St.  Mus.  p.  8o,  PL 

V,  Figs.  27,  28. 

1896.  P.  quinquelobus     Bather,    Am.    Geol.,  Vol.  XVII,  p.   184. 
Bather's  description  is  as  follows:    "Dorsal  cup  low;   pentagonal 

as  seen  from  ventral  surface,  the  angles  of  the  pentagon  being  radial  in 
position;  the  radial  facets  are  very  narrow,  the  radial  processes  corre- 
spondingly broad,  forming  the  concave  sides  of  the  pentagon ;  basals 
hidden  in  the  concavity  of  the  stem."  To  which  may  be  added:  surface 
of  plates  smooth ;  sutures  very  obscure,  only  visible  with  the  aid  of 
a  magnifier;  stem  round.  The  form  and  arrangement  of  the  plates  is 
similar  to  the  two  preceding  species.  No  plates  of  the  ventral  disc 
present. 

The  species  is  closely  related  to  P.  gorbyi  S.  A.  M.,*but  is  distin- 
guished from  that  species  by  its  shorter  cup  and  the  position  of  the 
basal  plates,  which  in  P.  gorbyi  are  visible  from  a  side  view  and  in 
this  species  are  concealed  in  the  basal  cavity. 

Locality :  f  The  species  is  represented  in   the  collections  of   this 

Museum  by  four  specimens,  P  8414  and  P  8827,  which  were  collected 

by  the  writer  in  the  clay  pockets  of  the  Niagaran  limestone  at  Romeo, 

Illinois.     These  specimens  are  silicified  and  in  a  good  state  of  preserva- 

*  17th  Rept.  Geol.  Ind.,  p.  640,  PI.  VI,  Figs.  17-20. 


Oct.,  1907. 


New  Crinoids  — '■  Slocom. 


281 


tion.  There  seems  to  be  no  reason  to  doubt  that  they  are  specifically 
identical  with  the  specimens  from  Tennessee  on  which  the  original 
description  was  based. 


Fig.  4.     Diagram  of  Stephanocrinus. 


Family  STEPHANOCRINIDA^E. 

STEPHANOCRINUS  Conrad. 

Only  one  species  of  this  genus  has  heretofore  been  recognized  in  the 
Chicago  Area.  Two  new  species  have  been  collected  by  the  writer  and 
are  here  described.  The  generic  characters  are  as  follows :  Basals  three, 
about  equal  in  size,  two  pen- 
tangular, one  quadrangular. 
Radials  five,  equal,  resem- 
bling the  forked  plates  of 
some  Blastoids.  These  prongs 
form  interradial  processes, 
and  between  them  are  situ- 
ated the  ambulacral  grooves 
leading  to  the  arms,  which 
rise  from  a  single  axillary 
costal  plate  situated  at  the 
end  of  the  sinus.  Oral  plates  five,  interradial  in  position  and  forming 
most  of  the  ventral  disc.  They  are  not  visible  in  a  side  view  of  the 
calyx.  They  join  the  inner  surface  of  the  radial  plates  and  extend  to 
the  top  of  the  interradial  processes.  Their  lateral  edges  are  in  contact 
below  the  ambulacral  grooves,  but  a  space  is  left  for  the  mouth  at  the 
center  of  the  ventral  disc.  The  anus  is  situated  between  the  posterior 
oral  plate  and  the  adjoining  process. 

This  genus  has  been  referred  to  the  Cystoids  and  Blastoids  by  some 
writers,  and  while  it  undoubtedly  has  some  characters  similar  to  both 
it  has  been  shown  to  be  a  Crinoid  by  Wachsmuth  and  Springer  on 
account  of  its  brachial  plates.  » 

Stephanocrinus  obconicus  sp.  nov.  Plate  LXXXIV,  Figs.  12,  13. 

The  dorsal  cup  is  obconical,  truncated  at  the  base,  sides  slightly  con- 
vex, forming  an  angle  of  about  30  degrees.  The  surface  of  the  plates 
is  apparently  smooth  or  finely  granulose,  following  the  curve  of  the 
calyx  except  near  the  proximal  end  of  the  basal  plates,  where  they  de- 
velop a  median  ridge  giving  a  triangular  form  to  the  base.  This  ridge 
is  most  prominent  at  the  base  and  rapidly  diminishes,  disappearing 


282  Field  Columbian  Museum  —  Geology,  Vol.  II. 

altogether  before  the  center  of  the  plate  is  reached.     Sutures  obscure, 
not  marked  by  grooves. 

Basal  plates  three,  about  equal  in  size.  Two  are  pentangular  and 
one  is  quadrangular.  Together  they  form  an  obconical  cup  comprising 
about  half  the  height  of  the  calyx,  triangular  at  the  base  and  circular 
at  the  top.  There  is  a  slight  circular  depression  in  the  center  of  the 
base  for  the  reception  of  the  column.  Radial  plates  five,  equal  in 
size  with  the  lateral  edges  produced  into  interradial  processes.  Height, 
aside  from  the  processes,  about  equal  to  that  of  the  basals.  The 
characters  of  the  vault  are  quite  obscure,  but  appear  to  correspond 
with  the  description  of  the  genus. 

This  species  is  based  on  a  single  silicified  specimen (Mus.  No.  P  8416) 
in  a  fairly  good  state  of  preservation.  Its  obconical  form  renders  it  so 
unlike  all  other  species  of  the  genus  that  comparison  with  them  seems 
to  be  superfluous.  The  following  measurements,  in  millimeters,  taken 
from  the  type  specimen,  may  be  of  use  for  comparison  in  case  other 
specimens  are  found. 

Diameter  at  base, 2.3  mm 

Diameter  at  top  of  basals, 5.5 

Diameter  at  top  of  calyx, 6.4 

Height  of  radials  aside  from  spines, 4.6 

Height  of  basals, 5.0 

Height  of  calyx, 9.6 

Length  of  spines, 1.6 

Locality:  Collected  by  the  writer  in  the  fall  of  1905  in  the  clay 
pockets  of  the  Niagaran  limestone  at  Romeo,  Illinois. 

Stephanocrinus  skiffi,  sp.  nov.     Plate  LXXXIV,  Figures  16-20. 

The  calyx  has  a  small  triangular  base.  It  expands  rapidly  to  the 
top  of  the  basals  and  moderately  from  that  point  on.  The  distal  edges 
of  the  radial  plates  are  excavated  for  the  reception  of  the  arms,  thus 
forming  five  interradial  processes.  The  plates  of  the  dorsal  cup  are 
ornamented  with  a  series  of  acute  prominent  striae.  These  striae  are 
oblique  at  and  below  the  upper  lateral  angles  of  the  radials,  longitudinal 
on  the  middle  of  the  radials  and  basals  and  transverse  on  the  lower 
part  of  the  basals.  Sutures  are  obscure  and  do  not  interrupt  the 
striae. 

Basal  plates  three,  about  equal  in  size,  one  quadrangular,  two  pent- 
angular. Together  they  form  a  funnel-shaped  cup,  triangular  at  the 
base  and  expanding  very  rapidly  to  the  top.  An  acute  angular  ridge 
extends  from  the  base  to  the  center  of  each  plate  where  it  becomes 
lost  in  the  longitudinal  striae.     The  basal  cup  comprises  about  half  the 


Oct.,   1907.  New  Crixoids  —  Slocom.  283 

height  of  the  calyx.  Radials  five,  equal,  sides  slightly  converging 
towards  the  base;  moderately  convex  longitudinally,  so  that  the  ven- 
tral view  of  the  calyx  is  subpentangular.  A  semicircular  excavation 
occupies  nearly  the  entire  distal  edge  of  the  radials,  and  the  processes 
thus  formed  are  rather  short  for  the  genus.  The  costals  are  not  pre- 
served in  the  type  or  any  of  the  specimens  at  hand.  The  inter- 
radials  or  orals  are  large  and  are  not  visible  in  a  side  view;  they 
comprise  the  greater  part  of  the  ventral  disc.  They  extend  to  the  top 
of  the  radial  processes,  and  rest  against  their  inner  faces.  Laterally 
they  connect  with  each  other,  but  leave  a  comparatively  large  round 
opening  for  the  peristome  in  the  center  of  the  disc.  The  deflected 
lateral  edges  form  the  ambulacral  groove  extending  from  the  arm 
bases  to  the  central  opening.  The  anal  opening  is  situated  at  the 
juncture  of  the  posterior  interradial  with  the  processes  of  the  two 
posterior  radials.  None  of  the  plates  which  covered  the  peristome, 
ambulacral  grooves  or  anal  opening  is  preserved. 

The  natural  casts  are  similar  in  form  to  the  exteriors,  but  slightly 
constricted  at  the  arm  bases  and  somewhat  shorter  in  proportion  to 
their  diameter.  The  interradial  processes  are  indicated  by  five  rather 
stout  protuberances  between  which  the  dorsal  cup  curves  gradually 
into  the  convex  ventral  disc.  A  large  circular  protuberance  in  the 
center  of  the  disc  indicates  the  size  and  position  of  the  peristome,  and 
a  small  one  rising  out  of  the  posterior  interradial  process  indicates  the 
anal  opening. 

Dimensions  of  the  type  are  as  follows: 

Natural  mold  Natural  cast 

Height  of  calyx,  6.7  mm.  Height  of  calyx,  4.5   mm. 

Height  of  basals,  3.3    "     Height  of  basals,  1.3     " 

Height  of  radials,  2.4    "    Height  of  radials,  2.4     " 

Height  of  processes,  1.0    "    Height  of  processes,  0.8     " 

Diameter  at  arm  bases,    5.0    "    Diameter  at  arm  bases,    2.9     " 
Diameter  at  top  of  basals,  4. 1    "    Diameter  at  top  of  basals,  3.0     " 
As  to  size,  form  and  pattern  of  ornamentation,  this  species  ap- 
proaches 5.  hammelli  S.  A.  M.  *  and  from  the  original  description  and 
figures  it  would  hardly  be  safe  to  separate  them.     Upon  comparison, 
however,  with  the  types  of  S.  hammelli,  which  are  in  the  paleontological 
collections   of  the  University  of  Chicago,  the  ornamentation  of  the 
plates  was  found  to  be  so  much  more  prominent  in  the  specimens  here 
described  as  to  warrant  specific  distinction.     The  striations  in  both 
species  are  so  grouped  as  to  form  geometric  figures.     For  instance,  the 
longitudinal  striae  on  the  right  posterior  radial  and  the  basal  on  which 
*  17th  Rept.  Geol.  Ind.,  p.  635,  PI.  VI,  Figs.  7-9. 


284 


Field  Columbian  Museum  —  Geology,  Vol.  IT. 


it  rests,  are  in  the  form  of  a  rhomb,  with  its  transverse  axis  equal 
to  the  width  of  the  radial  plate.  In  5.  skiffi  the  rhomb  consists  of  nine 
striae,  but  in  5.  hammelli  there  are  more  than  three  times  that 
number.  In  5.  hammelli  moreover  the  curvature  of  the  rhomb  con- 
forms to  the  general  curvature  of  the  calyx,  but  in  5.  skiffi  it  is  decid- 
edly convex  transversely  and  moderately  so  longitudinally  (PI. 
LXXXIV,  Fig.  16). 

The  type  specimen  (Mus.  No.  P  8479)  consists  of  a  natural  cast  and 
more  than  half  the  accompanying  mold,  both  in  an  excellent  state  of 
preservation.  Several  other  individuals  of  this  species  are  in  the 
collections. 

The  specific  name  is  proposed  in  honor  of  Mr.  Frederick  J.  V. 
Skiff,  Director  of  the  Museum. 

Locality:  Niagaran  limestone  of  the  spoil  heaps  of  the  Chicago 
Drainage  Canal  near  Lemont,   Illinois. 


Family  ZOPHOCRINID^E. 

ZOPHOCRINUS  S.  A.  Miller. 

Two  new  species  belonging  to  this  genus  were  collected  by  the  writer 
and  are  here  described.  This  genus  differs  from  all  other  crinoids  in 
that  the  calyx  contains  but  four  radial  plates ;  the  quadrangular  one 
is  somewhat  larger  than  the  others  and  is  probably  made  up  of  the 
right  and  left  posterior  radials  fused,  as  the  tetramerism  affects  the 
dorsal  cup  only;   the  dome  and  arms  are  pentameral. 


Br&i  £&  u  ova \mJ 


Fig.  5.    Outline  of  the  (i)  Posterior  and  (2)  Ventral  Views  of  the  Genotype  and  (3)  Diagram  of 
Zophocrinus.    (After  Bather.; 


The  plates  are  as  follows:  Basals  three,  two  equal,  one  larger; 
radials  four,  three  equal,  one  larger.  The  ventral  disc  is  composed 
of  five  orals,  the  posterior  oral  is  the  largest  and  the  two  anterior  orals 


Oct.,  1907.  New  Crixoids —  Slocom.  285 

are  the  smallest  and  are  not  in  contact  with  the  posterior  one;  anus 
unknown ;  five  groups  of  arms  are  situated  where  the  interoral  sutures 
meet  the  radials.  The  distal  edges  of  the  radials  are  thickened- on  their 
inner  side  and  are  pierced  by  pores.  The  presence  of  these  pores  has 
been  taken  by  some  writers  to  indicate  that  the  genus  might  belong 
to  the  cystoids,  but  for  the  present  it  is  considered  to  be  a  crinoid. 

Zophocrinus  globosus  sp.  nov.  Plate  LXXXV,   Figures   15-19. 

The  calyx  is  small,  in  the  form  of  a  prolate  spheroid,  truncated  at 
the  top.  The  natural  casts  are  subspherical,  slightly  flattened  on  six 
sides,  approaching  a  rounded  hexahedron.  The  plates  are  rather  thick 
and  smooth  or  possibly  finely  granulose,  convex,  slightly  sloping  towards 
the  sutures,  so  that  their  shape  and  arrangement  is  easily  studied. 

Basal  plates  three,  much  thicker  than  the  radials;  two  are  quad- 
rangular and  about  equal  in  size ;  the  other  is  pentangular  and  larger ; 
together  they  form  a  shallow  rounded  cup  with  a  slight  triangulation  at 
the  base  and  a  circular  depression  for  the  reception  of  the  column. 
Radials  four,  height  and  width  about  equal ;  three  are  pentangular,  the 
other  is  quadrangular;  their  sides  are  subparallel,  slightly  contracted 
at  either  end.  These  plates  have  a  decided  thickening  of  the  inner 
margin  of  their  distal  ends,  which  is  shown  by  a  deep  groove  on  the 
natural  casts.  The  ventral  disc  is  not  preserved  on  any  of  the  spec- 
imens studied. 

The  species  differs  from  the  other  species  of  the  genus  in  its  globose 
form,  its  relatively  short  radial  plates  and  its  rounded  base,  as  com- 
pared with  the  pear-shaped  body  and  attenuate  obconical  base  of  the 
other  species.  These  characters  are  stated  in  more  detail  on  a  later 
page. 

Locality :  Niagaran  limestone  of  the  spoil  heaps  along  the  Drainage 
Canal,  about  a  mile  and  a  half  east  of  Lemont,  Illinois. 

This  species,  while  it  cannot  be  said  to  be  abundant  in  this  Area,  is 
by  no  means  rare.  Four  specimens  were  collected  by  the  writer  in  the 
fall  of  1905  and  a  like  number  in  the  spring  of  1906.  The  specimens 
consist  of  natural  casts  with  more  or  less  of  the  accompanying  molds. 
The  Museum  number  of  the  type  specimen  is  P  8480. 

Zophocrinus  pyriformis  sp.  nov.  Plate  LXXXV,  Figures  12-14. 
The  calyx  is  broadly  pear-shaped,  truncated  at  the  top,  expanding 
rapidly  from  the  base  to  about  the  middle  of  the  radials,  from  which 
point  it  contracts  to  the  arm  bases.  The  surface  of  the  plates  is  finely 
granulose  and  moderately  convex,  sloping  towards  the  sutures;  this 
shallow  depression  indicates  the  position  of  the  sutures. 


286  Field  Columbian  Museum  —  Geology,  Vol.  II. 

The  basal  plates  are  three  in  number.  Together  they  form  an  ob- 
conical  cup  comprising  about  one-third  the  height  of  the  calyx.  Two 
are  quadrangular  and  equal  in  size,  the  other  is  pentangular  and  larger. 
The  proximal  end  of  each  plate  is  provided  with  a  decided  median 
ridge,  giving  a  triangular  base  to  the  cup  in  which  is  a  circular 
depression  for  the  reception  of  the  stem.  The  radial  plates  are  four, 
about  equal  in  size,  three  pentangular  and  one  quadrangular;  the 
distal  margins  are  thickened  and  beveled  towards  the  interior.  The 
beveled  edge  of  each  plate  is  pierced  by  pores,  the  exact  number  of 
which  cannot  be  determined  from  this  specimen. 

This  species  is  founded  on  a  single  silicified  specimen  (Mus.  No. 
P  8415),  having  the  dorsal  cup  complete  and  in  a  good  state  of  preser- 
vation, but  the  dome  is  missing.  In  form  it  appears  to  occupy  a 
position  between  that  of  Z.  howardi  and  Z.  globosus.  The  descrip- 
tion of  Z.  howardi*  is  as  follows:  "Body  subovate  or  pear-shaped, 
greatest  diameter  at  the  upper  third,  pointed  below,  length  more 
than  twice  the  diameter;  base  subhexahedral."  Z.  pyriformis  is 
distinguished  from  Z.  howardi  by  being  much  shorter  in  proportion  to 
its  greatest  diameter  and  by  the  form  of  the  base ;  also  the  opening 
formed  by  the  distal  edges  of  the  radial  plates  is  much  larger.  From 
Z.  globosus,  which  it  resembles  in  general  proportions,  it  differs  in  the 
form  of  the  base  and  general  outline  of  the  calyx. 

The  comparative  characters  of  the  three  species  may  be  shown  in 
tabular  form  as  follows: 

Ratio  of  F     m     f  b     e       Form  of  Position  of 

diameter  to  height      or  as        basal  cup      greatest  diameter 

Z.  globosus  6:7  Hemispherical     Wider  than  Near  middle 

high 

Z.  pyriformis  3 :4  Short  Wider  than  Near  middle 

triangular  high 

Z.  howardi  1  '.2  Long  Higher  than  Upper  third 

hexagonal  wide 

Locality:  The  type  specimen  (Mus.  No.  P  8415)  was  collected  by 
the  writer  in  the  clay  pockets  in  the  Niagaran  limestone  at  Romeo, 
Illinois. 

Examination  of  a  large  series  of  specimens  of  Z.  howardi  from  St. 
Paul,  Indiana,  showed  two  individuals  of  Z.  pyriformis. 

*  17th  Rept.  Geol.  Surv.  Indiana,  p.  643. 


Oct.,  1907.  New  Crinoids  —  Slocom.  287 

Order   IT.     FISTULATA. 

Family  GASTEROCOMID.^. 

ACHRADOCRINUS  Schultze. 

This  genus  was  originally  proposed  by  Schultze,  to  receive  a  species 
from  the  Devonian  rocks  of  the  Eifel,  Germany.  The  species  collected 
by  the  writer  and  here  described  is  the  first  American  species  to  be 
referred  to  the  genus.  The  original  description*  of  the  genus  is  as  fol- 
lows :  "The  composition  of  the  calyx  is  as  follows :  Basalia  (infrabasals) 
five,  equal,  pentagonal;  Parabasalia  (basals)  five,  four  equal,  pent- 
agonal, the  fifth  hexagonal;  Radialia  (radials)  five,  pentagonal,  alter- 
nating with  parabasalia  (basals) ;  Interradials  (anal  plate)  one,  resting 
on  the  horizontal,  truncated  edge  of  the  hexagonal  parabasal  (basal) 
directly  beneath  the  anal  opening. 

Ventral  dome,  arms  and  column  unknown.  The  base  is  pierced 
by  a  single  circular  canal." 

Genotype  Achradocrinus  ventrosus. 

To  the  above  description  of  the  radial  plates  may  be  added  the 
following,  as  the  characters  are  generic :  Radials  five,  shield-shaped ; 
three  regular  and  equal,  the  two  posterior 
ones  irregular,  deeply  excavated  for  the 
reception  of  the  anal  plate  which  they  en- 
close on  three  sides  by  meeting  above.  A 
prominent  articular  facet  occupies  the 
outer  side  of  the  radials  near  their  distal 
edges.  The  facets  are  provided  with  a 
ventral  groove  and  are  pierced  by  a  small 
canal  located  at  some  distance  from  the 
groove. 

In  referring  Achradocrinus  to  the  Gas-      blgb-   D'afranI  °!  ****** 

°  (After  Schultze). 

terocomidae    Schultze    compares    it    with 

Gasterocoma,  which  it  resembles  in  general  arrangement  of  the  plates 

and  position  of  the  anal  interradius,  but  from  which  it  differs  in  the 

form  of  the  basal  canal.     In   Gasterocoma  the  base  is  pierced  by 

a  quadrilobate  canal  and  in  Achradocrinus   by  a  circular,  central 

canal. 

So  far  as  is  known  to  the  writer,  all  genera  heretofore  referred  to 
the  Gasterocomidae  have  been  of  Devonian  age. 

♦Monographic  der  Echinodermen  des  Eifler  Kalkes,  p.  101. 


288  Field  Columbian  Museum  —  Geology,  Vol.  II. 

Achradocrinus  patulus  sp.  nov.   Plate  LXXXV,   Figures   1-4. 

Dorsal  cup  depressed,  obconical,  truncated  at  the  base,  somewhat 
inflated  on  the  posterior  side  so  that  the  symmetry  is  bilateral.  Sur- 
face of  the  plates  granulose  and  moderately  convex,  forming  shallow 
grooves  in  which  the  sutures  are  situated. 

Infrabasals  small,  forming  a  disc  which  barely  extends  beyond  the 
circumference  of  the  column.  The  disc  is  provided  with  a  central, 
circular  canal,  and  the  plates  appear  to  be  fused  as  the  sutures  are 
not  visible.  Basals  five,  four  equal  in  size  and  shape,  angular  above, 
the  posterior  larger  and  truncated  to  support  the  anal  plate.  Ra- 
dials  five,  three  shield-shaped  and  equal,  the  two  posterior  radials 
deeply  excavated  for  the  reception  of  the  anal  plate  which  they  en- 
close on  three  sides  by  meeting  above.  The  distal  edges  of  the  radials 
are  sharply  inflected  towards  the  center  of  the  vault.  A  prominent, 
semicircular,  articular  facet,  directed  outward,  occupies  more  than 
half  the  width  of  the  radials.  There  is  an  axial  canal  situated  at 
about  the  center  of  the  facet  and  a  wide,  shallow  ventral  groove  ex- 
tends from  the  facet  across  the  inflected  edge  of  the  radials.  The 
anal  plate  is  small,  subquadrangular,  its  lateral  edges  arched  and 
its  distal  edge  excavated  for  the  anal  opening.  It  rests  upon  the 
posterior  basal  and  between  the  posterior  radials.  The  anal  opening 
is  situated  in  line  with  the  arm  facets  directly  above  the  anal  plate 
and  below  the  lateral  extension  of  the  adjoining  radials.  The  opening 
is  directed  horizontally  and  is  surrounded  by  a  number  of  small  plates. 
Arms  unknown,  but  judging  from  the  articular  facets  they  appear  to 
be  widely  divergent  or  possibly  recumbent.  Tegmen  not  preserved. 
Column  circular  with  central  canal. 

The  species  here  described  is  referred  to  the  above  genus,  although 
differences  from  the  genotype  occur.  These  differences,  however, 
are  not  considered  to  be  of  generic  importance.  Schultze's  original 
figures  are  reproduced  for  comparison,  PI.  LXXXV,   Figs.   5-8. 

With  A.  ventrosus,  A.  patulus  compares  as  follows:  In  form  and 
arrangement  of  the  plates  the  two  species  are  similar,  likewise  in  the 
character  of  the  stem  and  the  articular  facets  with  their  ventral  grooves 
and  axial  canals.  In  A.  ventrosus,  however,  the  five  infrabasals  are 
distinct  and  form  a  shallow  cup  visible  in  a  side  view  of  the  calyx,  but 
in  A.  patulus  the  infrabasals  appear  to  be  fused  into  a  disc  and  incon- 
spicuous. The  type  specimen  of  A.  patulus  is,  however,  silicified  and 
it  is  quite  probable  that  the  basal  sutures  have  been  obliterated  in  the 
process  of  silicification.  The  anal  opening  in  both  species  is  situated 
between  the  distal  edge  of  the  anal  plate  and  the  lateral  extensions  of 
the  posterior  radials;  but  in  the  genotype  the  opening  is  directed 


Oct.,  1907,  New  Crinoids  —  Slocom.  289 

vertically  and  is  not  visible  in  a  side  view  of  the  calyx.  In  A. 
patulus,  however,  the  opening  is  in  line  with  the  center  of  the  arm 
facets,  directed  horizontally  and  visible  only  in  a  side  view  of  the 
calyx. 

Locality:  The  type  specimen,  Mus.  No.  P  8417,  is  a  silicified  dorsal 
cup  in  a  good  state  of  preservation.  It  was  collected  by  the  writer 
in  the  clay  pockets  of  the  Niagaran  limestone  at  Romeo,  in  the  fall  of 
1905- 

Family  CYATHOCRINID/E. 

HOMOCRINUS  Hall. 

No  members  of  this  genus  have  been  heretofore  reported  from  this 
area,  but  two  species,  H.  ancilla  and  H.  cylindricus,  were  collected  by 
the  writer  and  are  here  described.     The  generic  description  is  as  fol- 
lows: Calyx  dicyclic,  subcylin- 
drical  to  turbinate.     Infraba- 
sals   five;   basals  five;  radials 
five,  separated  on  the  posterior 
side   by  an  anal   plate.     The 
radianal  plate  is  situated  below 
the  right  posterior  radial  and 

between      the      right      anterior  Fig.  7-    Diagram  of  Homocrinus.    (After  Bather). 

radial  and  the  anal  plate ;  ven- 
tral sac  long  and  large ;  arms  bifurcating,  without  pinnules ;  stem  round. 
Distinguished  from  Dendrocrinus  by  the  proportionally  larger  infraba- 
sals   and   from   Poteriocrinus   by  the   arrangement   of   the   azygous 
plates. 

Homocrinus  ancilla  Hall,  Plate  LXXXV,  Figures  9-1 1. 

1879  Dendrocrinus  ancilla  Hall,  Trans.  Alb.  Inst.,   Vol.  X,  p.  9. 

1882  Dendrocrinus  ancilla  Hall,   nth  Geol.   Rept.   Ind.,  p.  271. 

1886  Homocrinus  ancilla  W.  &  Sp.,  Revis.  Paleocrinoidea,  Pt.  Ill, 
p.  220. 

Hall's  description  of  this  species  is  as  follows:  "Body  narrowly 
turbinate,  width  and  height  above  as  ten  to  twelve  or  ten  to  thirteen; 
contracted  between  the  arm  bases ;  upper  part  of  the  column  closely 
adhering  to  the  body,  the  five  minute  basal  plates  (infrabasals) scarcely 
distinguishable  from  the  segments  of  the  column  at  its  summit;  sub- 
radial  plates  (basals)  obscurely  angular  on  the  lower  face,  about 
three-fourths  as  wide  as  long,  very  gradually  expanding  in  width  from 
the  base,  and  supporting  on  their  upper  adjacent  sloping  faces  a  large 


290  Field  Columbian  Museum  —  Geology,  Vol.  II. 

hexagonal  interradial  plate,  and  this  supporting  a  single  radial,  from 
which  the  arms  take  their  origin.     Arms  unknown." 

A  detailed  description  of  specimens  from  the  Chicago  Area  is  as 
follows:  Calyx  narrowly  turbinate  or  trumpet-shaped;  arm  bases 
prominent  with  constrictions  between ;  surface  of  the  plates  smooth ; 
sutures  situated  in  small,  but  well-defined  furrows;  base  dicyclic. 

Infrabasal  plates  five,  equal  in  size,  pentagonal,  higher  than  wide. 
Basals  five;  height  and  width  about  as  4:3;  four  are. hexagonal  and 
the  posterior  one  is  heptagonal,  being  truncated  to  support  the  anal 
plate  on  its  distal  edge.  The  infrabasals  and  basal  plates  together  form 
a  deep  cup,  its  base  apparently  about  the  size  of  the  upper  joints  of  the 
column.  It  expands  very  moderately  until  the  middle  of  the  basals  is 
reached,  from  which  point  the  expansion  is  quite  rapid  to  the  arm  bases. 
Radial  plates  five,  very  much  thickened  in  the  middle  of  their  distal 
edges  to  form  the  prominent  facets  for  the  attachment  of  the  arms ; 
these  facets  occupy  about  half  the  width  of  the  plate.  The  right 
posterior  radial  is  smaller  than  the  others,  on  account  of  the  radianal 
plate  being  interposed  between  the  anal  plate  and  the  right  anterior 
radial ;  it  rests  on  two  of  the  basals  and  supports  the  right  posterior 
radial ;  it  is  quadrangular  in  form.  The  anal  plate  is  situated  in  line 
with  the  radials  and  rests  on  the  truncated  distal  side  of  the  posterior 
basal;  it  joins  the  left  posterior  radial  on  one  side  and  the  right  pos- 
terior radial  and  the  radianal  on  the  other. 

The  natural  casts  conform  in  a  general  way  with  the  outline  of 
the  outside  of  the  plates,  with  the  exception  of  the  base,  which  ter- 
minates in  a  point,  and  the  region  of  the  arm  bases,  which  is  quite  con- 
stricted on  account  of  the  thickening  of  the  distal  portions  of  the 
radial  plates.  The  greatest  diameter  of  the  natural  casts  is  at  the 
middle  of  the  radials,  but  that  of  the  outside  of  the  plates  is  at  the  arm 
bases. 

This  species  was  originally  described  from  the  Niagaran  shales  at 
Waldron,  Indiana,  and  while  the  Chicago  specimens  do  not  agree  in  all 
respects  with  the  original  description,  there  seems  to  be  little  doubt 
that  they  should  be  referred  to  this  species.  In  regard  to  the  size  of 
the  infrabasals  Hall's  description  and  figure  do  not  agree.  Moreover, 
many  characters,  some  of  which,  such  as  the  size  and  position  of  the 
anal  plates,  are  of  generic  importance,  are  incompletely  described 
or  are  omitted  altogether  by  Hall. 

Locality :  The  specimens  from  the  vicinity  of  Chicago  consist  of 
natural  casts  with  the  accompanying  molds.  The  species  was  col- 
lected by  the  author  in  the  spoil  heaps  along  the  Chicago  Drainage 
Canal  near  Lemont,  Illinois.     The  specimen  used  for  the  illustration 


Oct.,  1907.  New  Crinoids  —  Slocom.  291 

is  said  to  have  been  collected  at  Joliet,  Illinois,  and  is  in  the  collection 
of  the  Joliet  High  School. 

Homocrixus  cylindricus  Hall,  Plate  LXXXIV,  Figures  14,  15. 

1852  H.  cylindricus  Hall,   Pal.   N.  Y.,  Vol.    II,  p.   186,  PI.  XLI, 
Figs.  2  and  3. 
'  1859  Poteriocrinus  cylindricus  Hall,  Correct  List  of  N.  Y.  Fossils. 

1879  H.   cylindricus    W.   &.    Sp.,    Revision    Paleocrinoidea,    Pt. 
I,    p.    78.    Pt.    Ill,    p.    220. 

Calyx  subcylindrical,  gradually  enlarging  to  the  top  of  the  infraba- 
sals  and  slightly  constricted  at  the  arm  bases.  Surface  of  the  plates 
smooth  and  conforming  to  the  general  curve  of  the  calyx,  except  the 
radials  which  are  longitudinally  convex  at  the  arm  facets,  giving 
a  lobed  appearance  to  the  upper  part  of  the  calyx;  lobes  thick. 
Infrabasals  five,  equal,  pentagonal,  higher  than  wide,  forming  a  cup 
whose  height  and  width  are  about  equal.  Basals  four,  higher 
than  wide,  the  largest  plates  of  the  calyx.  The  posterior  basal  is 
heptagonal,  being  truncated  distally  for  the  support  of  the  anal  plate. 
It  is  somewhat  larger  than  the  other  four  which  are  hexagonal  and 
equal  in  size.  Radials  five,  wider  than  high ,  somewhat  smaller  than 
the  infrabasals.  The  articulating  facets  for  the  arms  occupy  nearly 
the  entire  distal  edge  of  the  plate.  The  right  posterior  radial  is  smaller 
than  the  others,  on  account  of  the  proximal  end  being  displaced  by  the 
radianal  plate.  The  radial  symmetry  is  disturbed  by  the  presence  of 
an  anal  plate  situated  between  the  two  posterior  radials  and  resting  on 
the  posterior  basal,  and  a  radianal  plate  is  situated  at  the  right  of  the 
anal,  resting  on  the  posterior  and  right  lateral  basal  plates  and  carrying 
on  its  distal  side  the  right  posterior  radial. 

The  species  occurs  in  this  locality  in  the  form  of  natural  casts  and 
molds.  Owing  to  the  comparative  thickness  of  the  plates  the  casts 
are  quite  different  in  shape  from  the  molds.  The  infrabasal  cup  is  in 
the  form  of  a  rapidly  expanding  pyramid.  Owing  to  the  convexity 
of  the  inner  surface  of  the  basal  plates  there  is  a  noticeable  constriction 
a  little  above  the  middle  of  the  cast  and  another  at  the  arm  bases. 
The^se  features  are  well  shown  in  PI.  LXXXIV,  Fig.  15.  Hall's  original 
description*  of  this  species  is  brief,  and,  judging  from  his  figures,  his 
specimens  were  not  very  well  preserved.  There  seems  to  be  little 
doubt,  however,  that  this  specimen  should  be  referred  to  this  species. 
The  species  was  described  from  the  Niagaran  shale  at  Lockport,  New 
York,  and,  so  far  as  is  known  to  the  writer,  has  never  been  reported 
from  any  other  locality. 
*  Pal.  N.  Y.,  Vol.  II,  p.  186. 


292  Field  Columbian  Museum  —  Geology,  Vol.  II. 

Locality:  Collected  by  the  writer  in  the  spoil  heaps  along  the 
Chicago  Drainage  Canal  about  1  ]/2  miles  east  of  Lemont,  Illinois.  (Mus. 
No.  P  8887.) 

Family  CROTALOCRINID^. 

CROTALOCRINUS     Austin. 
Crotalocrinus  cora  Hall,  Plate  LXXXVI,  Figs.  3  and  4. 

1868  Cyathocrinus  cora  Hall,  20th  Rept.  N.  Y.  St.  Mus.,  p.  324,  PI. 

XI,  Figs.  13,  14. 
1870  Cyathocrinus  cora    Hall,  20th  Rept.  N.  Y.   St.    Mus.    (Rev. 

Ed.),  p.  366,  PI.  XI,   Figs.   13,   14. 
1879  Cyathocrinus  cora  W.  &  Sp.,  Rev.  Paleocrin.,  Pt.  I,  p.  85. 
1881  Cyathocrinus  cora  S.  A.  M.,  Jour.  Cin.  Soc.  Nat.  Hist.,  Vol. 

IV,  p.  171. 
1900  Cyathocrinus  cora  Weller,  Bull.  4,  Nat.  Hist.  Surv.  Chicago 

Acad.  Sci.,  p.  62,  PI.  XIV,  Figs.  6-10. 
1900  Crotalocrinus  americanus  Weller,  ibid.  p.  143,  PI.  XIV,  Fig.  1. 
1902  Crotalocrinus  cora  Weller,  Jour.  Geol.,  Vol.  X,  p.  532,  PI.  III. 
This  species  is  abundant  at  various   localities  in  the  vicinity  of 
Chicago  and  at  Racine,  Wisconsin,  in  the  form  of  natural  casts,  but  it 
is  rarely  found  with  the  brachial  plates  preserved.     The  specimen  here 
figured  (Mus.  No.  P  8809)  shows  the  anterior  and  right  anterior  rays, 
complete  to  the  fourth  bifurcation  of  the  brachials,  and  part  of  the  left 
anterior  and  right  posterior  rays.     This  is  probably  the  most  complete 
specimen  of  this  species  yet  discovered.     The  specimen  consists  of  a  nat- 
ural cast  with  more  than  half  the  accompanying  mold.     Fig.  3  is  drawn 
from  a  "composition"  impression  taken  from  the  natural  mold.     Col- 
lected by  the  writer  in  the  upper  layers  of  the  Hawthorne  Quarry,  Chi- 
cago, May,  1906. 

Order    III.     CAMERATA. 
Family  PLATYCRINID^. 

■  PLATYCRINUS     Miller. 
Platycrinus  augusta  sp.  nov.  Plate  LXXXVI,  Figures  5-7. 

Dorsal  cup  subhemispherical,  sharply  constricted  above,  with  the 
base  produced  into  a  circular  facet  for  the  attachment  of  the  column. 
Pentangular  in  transverse  section  at  the  arm  bases,  circular  below. 
Plates  thin,  without  ornamentation,  conforming  to  the  curvature  of 
the  calyx;    sutures  not  in  furrows,   inconspicuous. 


Oct.,  1907.  New  Crinoids  —  Slocom.  293 

The  natural  cast  is  similar  in  form  and  proportions  to  the  outside 
of  the  calyx  without  the  radial  and  basal  facets.  The  transverse 
ridge  near  the  arm  bases  is  more  prominent  and  the  inner  surface 
of  the  plates  is  slightly  beveled  towards  the  edges,  so  that  the  position 
of   the  sutures  is  indicated  on  the  casts  by  indistinct  ridges. 

Basals  three,  two  pentangular  and  equal,  the  other  smaller,  quad- 
rangular. Together  they  form  a  cup  wider  than  high  and  with  a  small 
circular  base.  Radials  five, "about  equal  in  size,  three  pentangular, 
two  quadrangular.  The  radials  are  inflected  on  a  line  with  the  lower 
part  of  the  articular  facet  forming  an  obtuse  angular  transverse  ridge. 
The  articular  facets  are  small,  occupying  about  one-third  the  width 
of  the  plates.  They  are  circular  in  outline  with  a  deep  ventral  groove. 
One  axillary  costal  is  attached  to  each  articular  facet.  Column,  as 
indicated  by  the  basal  facet,  round  with  a  central  circular  canal. 
Arms  and  ventral  disc  not  preserved. 

The  type  specimen  (Mus.  No.  P  8895)  consists  of  a  natural  cast  of 
the  dorsal  cup  and  the  associated  natural  mold  nearly  complete. 
Figures  5  and  6,  Plate  LXXXVI,  are  drawn  from  a  rubber  impression 
of  the  natural  mold.  This  species  is  so  different  in  its  general  form 
from  any  other  species  of  this  genus  that  comparison  seems  superfluous. 
The  specific  name  is  proposed  in  honor  of  the  wife  of  the  writer. 

Locality :  Collected  by  the  writer  in  the  Niagaran  limestone  of  the 
spoil  heaps  along  the  Chicago  Drainage  Canal  near  Lemont,  Illinois. 


Family  BATOCRINIDiE. 

HABROCRINUS  Angelin. 

Calyx  obconical  to  urn-shaped;  composed  of  thick,  more  or  less 
ornamented  plates.      Arms,  two  to  each 
ray;    uniserial,  long,  heavy  and  simple 
throughout.     Base  monocyclic. 

Basals    three,    equal.     Radials    five, 
each  followed  by  two  costals.     Distichals 

two  to  six  to  each  ray  leading  up  to  the  ^ ^^O^^C^CI/v^. 
arms.  First  anal  plate  large,  situated 
between  the  two  posterior  lateral  radials. 
It  is  followed  by  three  plates  in  the  sec- 
ond row  and  five  in  the  third.  The  anal 
interradius  is  much  wider  than  the  other 
interbrachial  areas.  Fig- 8"  Diagram  of  mbrocHnus/ 

The  genus  Habrocrinus  together  with  Pionocrinus  was  created  in 


2Q4 


Field  Columbian  Museum  —  Geology,  Vol.  II. 


1 878  by  Angelin*  to  receive  a  number  of  species  from  the  Silurian  rocks 
of  Gotland,  Sweden.  It  has  been  recognized  in  the  Wenlock  limestone 
in  England,  and  Wachsmuth  and  Springer  described  two  species  from 
Indiana  which  they  referred  to  the  subgenus  Acacocrinus.  The  differ- 
ences between  Habrocrinus  and  Pionocrinus  are  as  follows:  In  Hab- 
rocrinus the  interbrachial  areas  consist  of  one  plate  resting  on  the 
superior  lateral  edges  of  the  radials,  followed  by  two  plates  in  each 
of  the  succeeding  rows;  in  Pionocrinus  the  first  interbrachial  plate 
is  large,  occupying  the  space  between  the  two  rays  from  the  superior 
lateral  edges  of  the  radials  to  the  inferior  edges  of  the  first  distichals. 
This  plate  is  followed  by  a  single  narrow  plate.  The  first  costals  in 
Habrocrinus  are  hexangular,  while  those  of  Pionocrinus  are  quadran- 
gular. These  differences  are  not  considered  to  be  of  generic  import- 
ance, so  that  Bather  and  Wachsmuth  &  Springer  place  the  species 
originally  referred  to  Pionocrinus  in  the  genus  Habrocrinus. 


Fig.  9.    Outline   of  Habrocrinus  ornattis  Ang. 
Posterior  Views.    (Alter  Angelin). 


Lateral  and 


Fig.  10.  Outline  of  Piono- 
crinus jarctus  Ang.  Lateral 
View.     (After  Angelin). 


Habrocrinus  differs  from  Periechocrinus  in  character  and  ornamen- 
tation of  the  plates  of  the  dorsal  cup ;  in  the  former  the  plates  are  thick, 
more  or  less  sculptured,  sutures  situated  in  deep  furrows;  in  the 
latter  the  plates  are  thin,  edges  not  beveled  and  position  of  sutures 
not  well  defined.  In  Habrocrinus  the  arms  are  strong  and  simple; 
in  Periechocrinus  they  are  slender  and  branching.  In  the  former 
the  palmers  are  not  present  in  the  dorsal  cup ;  in  the  latter  they  are 
present.  In  the  former  the  number  of  arms  is  two  to  each  ray,  in  the 
latter  it  is  four  or  more  to  each  ray. 

Of  the  fourteen  American  species  referred  to  Periechocrinus ,  four 
species,  P.  benedicti  S.  A.  M.,  P.  chicagoensis  Weller,  P.  howardi  S.  A.  M. 
and  P.  ornatus  Hall,  possess  characters  which  appear  to  necessitate 
their  removal  from  that  genus  to  Habrocrinus.  The  characters  referred 
to  are  as  follows :  The  absence  of  the  palmers  in  the  dorsal  cup,  reduc- 
ing the  number  of  arm  bases  from  four  to  two  in  each  ray,  and  the 
*  Iconographia  crinoideorum,  p.  3. 


Oct.,  1907.  New  Cricoids  —  Slocom.  295 

thick,  more  or  less  sculptured  plates  with  edges  beveled  forming 
furrows  in  which  the  sutures  are  situated.  As  none  of  these  species 
has  been  found  with  the  arms  preserved,  it  is  not  possible  to  state 
whether  they  are  simple  or  branched,  but  the  number  of  the  arm 
bases  and  the  thickness  and  ornamentation  of  the  plates  indicate 
their  affinity  with  Habrocrinus.  In  the  new  species  described  herewith 
both  the  typical  form  of  Habrocrinus  and  the  form  referred  to  Piono. 
crinus  are  found. 

Habrocrinus   benedicti  S.   A.   Miller,  Plate  LXXXVII,  Figs.  6-7. 

1892  Saccocrinus  benedictiS.  A.  M.,Adv.  Sheets,  18th  Rept.  Geol. 
Surv.   Ind.,  p.    28,  PI.  V,   Figs.   1-2. 

1894  Saccocrinus  benedicti  S.  A.  M.,  18th  Rept.  Geol.  Surv.  Ind., 
p.  283,  PI.  V,  Figs.  1-2. 

1902  Periechocrinus  chicagoensis  Weller,  Bull.  4,  Nat.  Hist.  Surv., 
Chicago  Acad.  Sci.,  p.  131,  PI.  XIII,  Figs.  7-8. 

The  specimens  described  by  S.  A.  Miller  as  Saccocrinus  benedicti 
had  the  plates  preserved,  so  that  their  form  and  ornamentations 
were  well  shown.  The  specimens  were  from  St  Paul,  Indiana. 
Periechocrinus  chicagoensis  was  described  by  Weller  from  natural 
casts  from  Chicago,  no  specimens  showing  the  ornamentation  of  the 
plates  having  at  the  time  been  reported. 

In  the  summer  of  1906  the  writer  was  fortunate  enough  to  find  a 
natural  cast  of  P:  chicagoensis  accompanied  by  a  large  part  of  the  nat- 
ural mold.  Upon  taking  an  impression  of  this  mold  a  great  simi- 
larity with  P.  benedicti  was  at  once  apparent,  and  upon  further  study  of 
the  two  forms  there  appeared  little  reason  to  doubt  that  they  were 
specifically  identical.  As  Miller's  species  has  about  ten  years  priority, 
P.  chicagoensis  Weller  will  thus  become  a  synonym.  Wachsmuth  & 
Springer  consider  H .  benedicti  to  be  a  synonym  of  H.  ornatus.  This 
view  is  not  held  by  many  other  authors  and  a  comparison  of  the 
type  of  H.  benedicti  with  the  drawings  of  H.  ornatus  would  seem  to 
leave  little  room  to  doubt  that  they  are  distinct. 

Locality:  Niagaran  limestone  of  the  spoil  heaps  along  the  Chicago 
Drainage  Canal  near  Lemont,  Illinois.  The  specimen  here  figured 
has  the  Museum  number  P8893. 

The  bibliography  of  the  two  other  species  transferred  to  Habrocrinus 
is  here  given,  although  they  have  not  been  reported  from  this  Area. 

Habrocrinus  howardi  S.  A.  Miller. 

1892  Saccocrinus  howardi  S.  A.  M.,  Adv.  Sheets,  18th  Rept.  Geol. 
Surv.  Ind.,  p.  29,  PI.  V,  Figs.  3-5. 


296  Field  Columbian  Museum  —  Geology,  Vol.  II. 

1894  Saccocrinus  howardi  S.  A.  M.,  18th  Rept.  Geol.  Surv.  Ind., 

p.  284,  PI.  V,  Figs.  3-5. 
1897  Periechocrinus  howardi  W.  &  Sp.,  N.  Am.  Crin.  Cam.,  Vol. 

II,  p.  529. 
Niagara  Group,  St.  Paul,  Indiana. 

Habrocrinus  ornatus  Hall. 

1875  Saccocrinus   ornatus  Hall,  Pal.  Ohio,  Vol.  II,  p.  126,  PI.  VI, 

Figs.  7-9. 
1 88 1  Periechocrinus  ornatus  Wachsmuth  &    Springer,    Rev.    Pal- 

aeocr.,  Pt.  II,  p.  132. 
1897  Periechocrinus    ornatus    Wachsmuth    &    Springer,    N.    Am. 

Crin.  Cam.,  Vol.  II,  p.  527,  PI.  L,  Figs.  3a-b,  and  PI.  LI, 

Fig.  7. 
Niagara  group,  Yellow  Springs,  Ohio. 

Habrocrinus   farringtoni  sp.  nov.      Plate  LXXXVII,    Figs.    1-5. 

The  calyx  is  urn-shaped,  with  an  expanded  hexagonal  base.  The 
dome  is  not  preserved.  The  plates  of  the  dorsal  cup  are  thick,  depressed 
in  the  center,  with  low  nodes  near  the  angles.  The  sutures  are  sit- 
uated in  deep  furrows  formed  by  the  beveled  edges  of  the  plates.  No 
radial  ridges  are  found.  The  natural  casts  have  a  pronounced 
tubercle  near  the  center  of  the  radial  and  first  anal  plates,  indicating 
a  depression  on  the  inner  side  of  the  plates,  but  no  corresponding 
elevation,  on  the  exterior  of  the  plates,  is  shown  in  the  natural  mold. 
The  natural  casts  are  pyriform,  pointed  below  and  truncated  above, 
somewhat  constricted  between  the  prominent  arm  bases.  Arms, 
judging  from  the  arm  bases,  two  to  each  ray. 

Basals  three,  equal,  forming  a  shallow  hexagonal  cup.  Radials 
five,  height  and  width  about  equal ;  the  two  anterior  laterals  heptag- 
onal,  the  others  hexagonal.  First  costals  hexagonal,  about  half  the  size 
of  the  radials;  second  costals  smaller  than  the  first,  pentagonal,  axil- 
lary, bearing  the  distichals  upon  their  superior  edges.  First  distichals 
about  twice  as  high  as  wide.  Higher  plates  of  the  rays  not  known. 
First  interbrachials  hexagonal,  equal  in  size  or  slightly  larger  than  the 
first  costals;  they  are  followed  by  two  somewhat  smaller  plates,  and 
these  by  two  still  smaller  which  join  with  the  plates  of  the  dome.  No 
interdistichal  plates  visible.  The  anal  interradius  has  nearly  the 
combined  width  of  one  of  the  rays  and  two  interbrachial  areas.  The 
first  anal  plate  is  situated  between  the  two  posterior  radials,  resting  on 
the  basals.     It  is  heptagonal  in  form  and  from  its  superior  edge  extends 


Oct.,  1907.  New  Crinoids  —  Slocom.  297 

a  row  of  three  or  more  plates,  gradually  diminishing  in  size;  these 
anal  plates  are  similar,  in  size  to  the  corresponding  radial,  costal  and 
distichal  plates;  on  either  side  of  the  anal  plates  is  a  series  of  plates 
similar  to,  but  slightly  smaller  than,  those  of  the  interbrachial  areas, 
with  the  exception  that  there  are  three  in  the  third  row  instead 
of  two. 

This  species  somewhat  resembles  H.  benedicti  S.  A.  M.  in  general 
appearance,  but  it  is  distinguished  from  that  species  by  having  a  more 
shallow  and  expanded  basal  cup.  The  diameter  of  the  calyx  is  greater 
in  proportion  to  its  height  in  H.  farringtoni  than  in  H.  benedicti,  and 
both  the  constriction  below  the  arm  bases  and  the  second  and  third 
distichals  are  wanting  in  H.  farringtoni.  In  the  form  of  the  calyx 
and  the  ornamentation  of  the  plates  H.  farringtoni  resembles  H.  lemon- 
tensis,  but  they  are  distinguished  by  the  shape  of  their  first  costals 
and  by  the  number  and  shape  of  the  plates  in  the  interbrachial  areas. 

The  type  specimen  of  H.  farringtoni,  on  which  this  description  is 
based,  consists  of  a  natural  cast  of  the  dorsal  cup  accompanied  by  a 
portion  of  the  natural  mold.  The  sutures  are  well  defined  on  both 
cast  and  mold.  The  mold  comprises  two  rays,  one  interbrachial 
area  and  more  than  half  the  anal  interradius.  An  impression  taken 
from  this  mold  gives  the  external  form  of  the  calyx  and  the  surface 
markings  of  the  plates.  As  the  basal  plates  are  missing  from  this  mold, 
the  impression  of  a  mold  in  the  collection  of  the  University  of  Chicago 
is  also  figured,  Plate  LXXXVII,  Figs.  1  and  2.  The  type  is  somewhat 
crushed,  thus  giving  a  wider  appearance  in  proportion  to  its  height 
than  is  natural. 

The  specific  name  is  proposed  in  honor  of  Dr.  O.  C.  Farrington, 
Curator  of  the  Department  of  Geology  of  the  Museum. 

Locality :  This  species  is  represented  in  the  Museum  collections  by 
the  type  specimen  P  8474,  and  a  natural  cast,  P  8949.  These  were 
collected  by  the  writer  in  the  Niagaran  limestone  of  the  spoil  heaps 
along  the  Chicago  Drainage  Canal  about  a  mile  east  of  Lemont,  Illinois, 
one  in  the  fall  of  1905  and  one  in  the  spring  of  1906.  The  specimen 
in  the  collection  of  the  University  of  Chicago  is  from  the  same 
locality. 

Habrocrinus  lemontensis  sp.  nov.  Plate  LXXXVII,  Figs-.  8-10. 
The  calyx  is  urn-shaped  with  an  expanded  hexagonal  base ;  mod- 
erately constricted  between  the  prominent  arm  bases,  giving  a  pentag- 
onal section  to  the  dorsal  cup.  The  dome  is  not  preserved.  The 
plates  of  the  dorsal  cup  are  thick  and  depressed  with  nodes  near  the 
angles  of  the  plates.     The  sutures  are  situated  in  deep  furrows  formed 


298  Field  Columbian  Museum  —  Geology,  Vol.  II. 

by  the  beveled  edges  of  the  plates.  No  radial  ridges  are  observed. 
The  natural  cast  is  turbinate,  pointed  below  and  truncated  above, 
with  prominent  arm  bases.  Arms,  judging  from  the  arm  bases,  two  to 
each  ray. 

Basals  three,  equal  in  size,  forming  a  shallow  cup  with  an  hexag- 
onal outline.  Radials  five,  height  and  width  about  equal,  the  two 
anterior  laterals  heptagonal,  the  others  hexagonal,  in- contact  except 
at  the  posterior  side  where  they  are  separated  by  the  first  anal  plate. 
First  costals  quadrangular,  height  and  width  about  equal,  much 
smaller  than  the  radials.  Second  costals  about  the  size  of  the  first, 
wider  than  high,  pentangular,  axillary,  supporting  the  distichals  upon 
their  sloping  edges.  Distichals  comparatively  large,  two  or  more  to 
each  ray.  The  first  interbrachial  plate  is  intermediate  in  size 
between  the  radials  and  the  first  costals ;  it  is  nine-sided  and  occupies 
the  space  from  the  sloping  superior  edges  of  the  radials  to  the  inferior 
edges  of  the  distichals ;  it  supports  a  narrow  plate  upon  its  upper  edge. 
No  interdistichals  are  observed.  The  anal  interradius  is  considerably 
wider  than  the  interbrachial  areas.  The  first  anal  plate  is  heptagonal, 
resting  on  the  basals  between  the  posterior  lateral  radials.  It  is 
followed  by  three  plates  in  the  second  row  and  by  five  in  the  two 
succeeding  rows. 

In  the  arrangement  and  relative  size  of  the  plates  this  species 
closely  resembles  H.  (Pionocrinus)  farctus  Angelin  *  (See  Fig.  10),  but 
that  is  a  very  small  species  and  the  plates  are  moderately  convex  and 
without  sculpturing.  The  distinguishing  characters  between  this 
species  and  H.  farringtoni  are  discussed  under  that  species. 

The  type  specimen  (  Mus.  No.  P  9628  )  consists  of  a  somewhat 
weathered  natural  cast  with  a  portion  of  the  accompanying  natural 
mold.  The  mold  comprises  the  basal  cup  in  good  condition,  three 
radials  and  the  first  anal  plate  practically  complete  and  the  lower  half 
of  the  other  two  radials ;  in  two  of  the  rays  the  costals  and  one  of  the 
distichals  are  preserved  with  the  enclosed  interbrachial  area.  The 
impression  from  this  mold  gives  the  general  form  of  the  exterior 
of  the  dorsal  cup  and  the  ornamentation  of  the  plates.  The  form 
of  more  than  half  of  the  plates  can  be  traced  on  the  natural  cast,  so 
that  the  characters  of  the  species  can  be  ascertained.  The  pits  on  the 
basal  and  radial  plates,  shown  in  PI.  LXXXVII,  Figs.  8  and  9,  are 
caused  by  protuberances  in  the  natural  mold.  These  protuberances 
appear  to  be  carbonate  of  lime  deposited  after  the  original  crinoid 
had  been  dissolved  out,  and  probably  have.no  connection  with  the 
ornamentation  of  the  plates. 

* Iconographia  Crinoideorum,  p.   5,  PI.  XVI,  Fig.   23. 


Oct.,  1907. 


New  Crinoids  —  Slocom. 


299 


Locality :  The  species  is  represented  by  a  single  individual  collected 
by  the  writer  in  the  fall  of  1905,  in  the  Niagaran  limestone  in  the  spoil 
heaps  along  the  Chicago  Drainage  Canal,  about  one  mile  east  of 
Lemont,  Illinois. 


¥% 


Family  THYSANOCRINID^. 

THYSANOCRINUS  Hall. 

Weller's  description*  of  this  genus  is  as  follows: — 
"Calyx  subglobose,  urn  or  bell-shaped,  the  rays  marked  by  more  or 
less  conspicuous  ridges;  the  surface  of  the  plates  smooth,  or  variously 
ornamented.     Infrabasals  five  small,  barely  extending  beyond  the 
column,  or  entirely  hidden  by 
it.     Basals  five,  four  of  them 
equal  and  angular  above ;  the 
fifth  truncated  and  support- 
ing a  large  anal  plate.     Radi- 
als   considerably  larger  than 
the    costals,    their    proximal 
sides   distinctly  angular,  the 
lateral    faces    comparatively 
short.    Costals  two.    Distich- 
als  two  or  three  in  each  series. 
In   some   cases   palmers  are 
also  present,  the  axillary  dis- 
tichal  giving  rise  on  the  inter- 
radial  side  to  an  armlet  for 
the  most  part  included  in  the 

calyx  and  on  the  other  side  of  the  main  arm.  Four  of  the  first  inter- 
brachials  large,  angular  below,  resting  upon  the  sloping  upper  corners 
of  the  two  radials  and  against  the  costals;  two  plates  in  the  second 
row,  often  followed  by  smaller  ones  above  which  connect  with  the 
plates  of  the  disc.  The  anal  side  considerably  wider,  the  first  plate 
large,  hexagonal,  resting  upon  the  truncated  posterior  basal,  three 
plates  in  the  second  row  and  smaller  ones  above.  In  some  species 
an  uninterrupted  row  of  anal  plates  extends  to  the  anal  opening. 
Interdistichals  generally  represented  and  rather  large.  Column 
round  or  obtusely  pentangular." 

Thysanocrinus  campanulatus  sp.  nov.  Plate  LXXXV,  Figs.  20-23. 
The  calyx  is  bell-shaped,  expanding  very  rapidly  above  the  top  of 
*  Bull.  IV,  Pt.  I,  Nat.  Hist.  Surv.,  Chicago  Acad.  Sci.,  p.  70. 


Fig.  11.    Diagram  of  Thysanocrinus. 


300  Field  Columbian  Museum  —  Geology,  Vol.  II. 

the  radial  plates.  The  diameter  of  the  dorsal  cup  at  the  arm  bases 
is  about  one-half  greater  than  the  height  of  the  cup.  The  dorsal  cup 
is  ornamented  with  series  of  prominent  rounded  ridges.  The  ridges 
begin  near  the  middle  of  the  lower  margins  of  the  basal  plates  at  the 
juncture  with  the  column  and  extend  to  the  center  of  the  plate. 
At  this  point  they  bifurcate  and  pass  to  the  center  of  the  radials 
where  they  join  the  ridges  from  the  basals  on  either  side.  From 
the  center  of  the  radials  the  ridges  follow  the  median  line  of  the  radials 
and  costals  to  the  middle  of  the  axillary  costal  where  they  again  bifur- 
cate and  follow  the  distichals  up  to  the  arm  bases.  Another,  less 
conspicuous  ridge  connects  the  centers  of  the  posterior  lateral  radials 
crossing  the  first  anal  plate.  Surface  of  all  plates,  not  ornamented  with 
the  ridges,  smooth  and  moderately  convex.  Sutures  not  situated  in 
grooves.  In  the  natural  casts  the  dorsal  cup  is  broad  and  flat  at  the 
base  and  curves  abruptly  upward  at  about  the  middle  of  the  basal 
plates;  it  expands  moderately  up  to  the  middle  of  the  radials,  where 
a  slight  constriction  occurs,  and  above  this  constriction  the  expansion 
is  very  rapid  until  at  the  arm  bases  the  plates  are  nearly  at  right  angles 
to  the  axis  of  the  calyx.     Ventral  disc  not  preserved. 

Infrabasals  five,  small,  scarcely  extending  beyond  the  columnar 
facet.  Basals  five,  large,  forming  with  the  infrabasals  a  shallow  cup ; 
the  posterior  basal  is  heptagonal  and  larger  than  the  others  which  are 
hexagonal.  Radials  five,  larger  than  the  basals;  the  two  posterior 
laterals  are  hexagonal  and  the  rest  are  heptagonal.  First  costals 
hexagonal,  less  than  half  the  size  of  the  radials.  Second  costals 
axillary,  pentagonal  or  hexagonal.  In  some  cases  the  interdistichal 
appears  to  join  the  axillary  costal.  Distichals  two  or  more  in  each 
series.  First  interbrachials  are  hexagonal,  intermediate  in  size  between 
the  radials  and  first  costals ;  they  are  followed  by  three  or  more  rows 
of  two  plates  each,  diminishing  in  size  upward.  Interdistichals  pres- 
ent, but  in  the  specimens  at  hand  only  the  first  plate  is  preserved; 
this  appears  to  be  hexagonal  or  heptagonal.  The  anal  interradius 
is  wider  than  the  interbrachial  areas.  The  first  anal  plate  is  hexagonal, 
smaller  than  the  radials ;  it  rests  on  the  distal  edge  of  the  posterior 
basal  and  separates  the  posterior  lateral  radials;  it  supports  on  its 
distal  edge  a  row  of  plates,  diminishing  in  size,  which  lead  up  to  the 
vault ;  the  space  between  this  row  of  plates  and  the  posterior  lateral 
rays  is  filled  with  smaller  plates. 

In  its  general  form  and  proportions  this  species  is  so  unlike  all  other 
species  of  this  genus  that  it  will  be  easily  recognized. 

The  type  specimen,  P  889 1 ,  was  collected  by  the  writer  in  the  spring 
of  1906.     It  consists  of  a  nearly  perfect  natural  cast  of  the  dorsal 


Oct.,  1907.  New  Crinoids  —  Slocom.  301 

cup  accompanied  by  a  natural  mold  of  which  a  part  of   the   base 
is  missing. 

Locality :   Niagaran  limestone  of  the  spoil  heaps  along  the  Chicago 
Drainage  Canal  near  Lemont,  Illinois. 


Family  CALYPTOCRINID/E. 

EUCALYPTOCRINUS   Goldfuss. 
Eucalyptocrinus  obconicus     Hall,  Plate  LXXXVI,  Figures   1-2. 

1867  E.  obconicus  Hall,  20th  Rept.  N.  Y.  St.  Mus.,  p.  323,  PI.  XI, 
Fig.  1. 

1870  E.  obconicus  Hall,   20th  Rept.   N.  Y.  St.  Mus.,  Rev.  Ed., 
p.   365,   PI.   XI,   Fig.    1. 

1885  E.  obconicus  Wachsmuth  &  Sp.,  Rev.  Palaeocr.  Pt.  Ill,  p. 133. 

1897  E.  obconicus  Wachsmuth  &  Sp.,  N.  Am.    Crin.    Cam.,  Vol. 
I.,p.353,Pl.LXXXIII,Fig.  13. 

1900  E.  obconicus  Weller,  Bull.  4,  Nat.  Hist.  Surv.,  Chicago  Acad. 
Sci.,  p.  109,  PI.  VII,  Fig.  8. 

Dorsal  cup  obconical,  truncated  at  the  base  by  the  attachment  for 
the  column ;  height  nearly  twice  its  diameter  at  the  arm  bases ;  grad- 
ually and  regularly  expanding  from  the  size  of  the  column  at  its  base 
to  the  arm  bases  where  it  attains  its  greatest  diameter!  The  plates 
are  thicker  in  the  central  portion  than  at  the  edges,  so  that  both  their 
inner  and'  outer  surfaces  are  convex.  The  outer  surface  of  the  plates 
is  smooth  and  slopes  gently  towards  the  sutures.  The  natural  cast  is 
similar  in  outline  to  the  exterior  of  the  dorsal  cup,  but  it  is  pointed  at 
the  base.  The  position  of  the  sutures  is  indicated  by  low  angular  ridges 
which  are  formed  by  the  convexity  of  the  inner  surface  of  the  plates. 

Basals  four,  three  pentagonal,  one  hexagonal,  long  and  narrow. 
Together  they  form  a  cup,  height  and  width  about  equal.  Radials 
five,  the  largest  plates  in  the  calyx;  four  heptagonal,  the  other  hexag- 
onal, about  equal  in  size  and  nearly  twice  as  high  as  wide.  First  cos- 
tals  quadrangular,  higher  than  wide,  proximal  and  lateral  edges  arched, 
distal  edges  much  narrower  than  the  proximal  ones.  Second  or  axial 
costals  are  in  the  form  of  a  regular  pentagon,  somewhat  smaller  than 
the  first  costals.  Distichals  four  to  each  ray.  The  first  pair  hexagonal, 
in  contact  with  each  other  and  about  the  size  of  the  second  costals 
upon  which  they  rest.  The  second  pair  is  very  small.  First  inter- 
brachials  ten-sided,  about  twice  as  high  as  wide  and  next  to  the  radials 
in  size.  These  are  followed  by  two  long  narrow  plates,  with  their 
longest  edges  in  contact.     Interdistichals  small,  angular  below  and 


302  Field  Columbian  Museum  —  Geology,  Vol.  II. 

resting  upon   the  short,  sloping  edges  of  the  first  distichals  and  be- 
tween the  second  distichals. 

Arms  and  ventral  disc  not  preserved. 
The  following  dimensions  are  given  for  comparison.     Those  of  the 
type  are  taken  from  the  cut,  those  of  this  specimen  from  the  cast. 


This  specimen 

Typ 

e  specimen 

Length  of  dorsal  cup, 

37-5  mm- 

19 .0 

Diameter  at  arm  bases, 

18.2 

J3-5 

Diameter  at  top  of  radials, 

1 1 . 1 

8.0 

Height  of  radials, 

12.5 

5-2 

Height  of  basals, 

7-7 

* 

2-5 

Owing  to  the  fact  that  this  specimen  is  somewhat  distorted,  the 
dimensions  of  the  diameters  as  given  are  estimated.  The  actual 
measurements  are  as  follows : 

The  longer  and  shorter  diameters  at  arm  bases  are  22.15  and  14.3 
respectively. 

The  longer  and  shorter  diameters  at  top  of  radials  are  12.9  and  9  .  3 
respectively. 

The  specimen  here  described  (  Mus.  No.  P  8879  )  consists  of  a 
practically  complete  natural  cast  accompanied  by  a  portion  of  the  mold. 
The  mold  comprises  one  complete  ray,  a  portion  of  two  others  and  part 
of  three  interbrachial  areas.  So  far  as  known  to  the  writer,  this  is 
the  first  specimen  of  this  species  in  which  the  external  characters 
of  the  plates  have  been  described  or  figured.  This  specimen  differs 
from  the  type  as  figured  by  Hall  in  several  particulars,  and  if  other 
specimens  should  be  found  showing  these  characters- to  be  constant,  it 
may  be  advisable  to  consider  this  a  new  species.  This  specimen  is 
about  twice  the  length  of  the  type  and  somewhat  more  slender.  The 
basals,  radials,  first  costals  and  first  interbrachials  are  much  higher 
in  proportion  to  their  width.  In  the  type  the  sutures  between  the  first 
costals  and  first  interbrachials  are  straight,  but  in  this  specimen  they 
are  arched,  with  the  convex  side  towards  the  interbrachial. 

This  species  is  distinguished  from  all  other  species  of  the  genus 
by  the  absence  of  a  basal  cavity. 

Locality:  Niagaran  limestone  of  the  spoil  heaps  along  the  Chicago 
Drainage  Canal  near  Lemont,  Illinois. 


Oct.,  1907.  New  Crinoids  —  Slocom.  303 

Previous  to  the  present  publication  there  have  been  described 
from  the  Chicago  Area  a  total  of  62  species  of  crinoids  divided  among 
26  genera.  A  complete  list  of  these  was  given  by  Weller  in  1900.* 
Two  years  later  Weller  obtained  a  specimen  which  showed  that 
Cyathocrinus  cora  Hall  and  Crotalocrinus  americanus  Weller  were  one 
and  should  be  known  as  Crotalocrinus  cora  Hall,  f  thus  making  the 
number  of  species  61.  The  species  obtained  by  the  present  writer 
increase  the  total  number  of  species  of  crinoids  known  from  the  Chicago 
Area  to  75  and  that  of  the  genera  to  30.  A  full  list  of  these  follows. 
In  addition  it  may  be  noted  that  several  specimens  which  were 
associated  with  those  here  described  and  which  are  evidently  new 
species  proved  too  fragmentary  for  description.  Should  better  speci- 
mens of  these  be  obtained,  three  or  more  new  species  and  at  least  one 
new  genus  may  be  added  to  the  list. 

*  Bull.  4,  Nat.  Hist.  Surv.,  Chicago  Acad.  Sci.,  Pt.  I. 
t  Jour.  Geol.,  Vol.  X,  pp.  532-4. 


LIST  OF  CRINOIDS  OF  THE  CHICAGO  AREA. 
Order  I.    LARVIFORMIA. 

Family  Pisocrinid^e. 

Pisocrinus  benedicti,  S.  A.  M. ;  P.  gemmiformis,  S.  A.  M. ;  P.  quinquelobus, 
Bather. 

Family  Stephanocrinid^e. 

Stephanocrinus  obconicus,  Slocom;  5.  osgoodensis,  S.  A.  M. ;  S.  skiffi, 
Slocom. 

Family  Zophocrinid^e. 

Zophocrinus  howardi,  S.  A.  M.;   Z.  globosus,  Slocom;  Z.  pyriformis, 
Slocom. 

Family  Heterocrinid^e. 

Myelodactylus  bridge poriensis,  S.  A.  M. 

Order  II.     FISTULATA. 

Family  Gasterocomid^e. 
Achradocrinus  patulus,  Slocom. 

Family  Cyathocrinid^e. 

Homocrinus  ancilla,  Hall;//,  cylindricus,  Hall. 
Cyathocrinus  turbinatus ,  Weller;  C.  vanhorni,  S.  A.  M. 
Botryocrinus  polyxo,  Hall. 
Ampheristocrinus  dubius,  Weller. 

Family  Crotalocrinid^e. 
Crotalocrinus  cora,  Hall. 


Order  III.     CAMERATA. 

Family  Platycrinid^e. 

Platycrinus  augusta,  Slocom;  P.  dubius,  Weller. 
Marsupiocrinus  chicagoensis,  Weller. 

3°4 


Oct.,  1907.  New  Crinoids  —  Slocom.  305 

Family  Batocrinid^e. 

Habrocrinus  benedicti,  S.  A.M.;  H.farringtoui,  Slocom;  H .  lemontensis 

Slocom. 

Periechocrinus  egani,  S.  A.  M.;  P.  infelix,  W.  &  M.;  P.  marcouanus, 

W.  &  M. ;  P.  necis,  W.  &.  M. ;  P.  urniformis,  S.  A.  M. 

Family  Thysanocrinid,e. 

Thysanocrimis  campanulatus,   Slocom;    T.    egani,    S.  A.  M. ;    T '.  occi- 
dentalism Hall;  T.  pentangularis ,  Hall. 
Cyphocrinus  chicagoensis ,  Weller. 
Gazacrinus  major,  Weller;  G.  minor,  Weller. 

Lampterocrinus  dubius,  Weller;   L.  inflatus,  Hall;   L.  r obust us,  Weller; 
L.  subglobosus,  Weller. 
Siphonocrinus  nobilis,  Hall. 

Family  Rhodocrinid/e. 

Arclueocrinus  depressus,  Weller. 
Lyriocrinus  melissa,  Hall. 

Family  Melocrinid^e. 

Macrostylocrinus  obconicus,  Weller;    M.  semiradiatus  Hall;  M.  stri- 

atus,  Hall;  M.  subglobosus,  Weller. 

Melocrinus  obpyramidalis,  W.  &  M. 

Corymbocrinus  chicagoensis,  Weller;  C.  niagarensis,  Weller. 

Family  Calyptocrinid^e. 

Eucalyptocrinus  asper,  Weller;  E.  crassus,  Hall;  E.  depressus,  S.  A.  M. ; 
E.  egani,  S.  A.  M.  ;  E.  inornatus,  Weller;  E.  magnus,  Worthen;  E. 
nodulosus,  Weller.;  E.  obconicus,  Hall;  E.  ornatus,  Hall;  E.  rotundus, 
S.  A.  M.;  E.  turbinatus,  S.  A.  M. 

Callicrinus  biforcatus,  Weller;  C.  bilobus,  Weller;  C.  cornutus,  Hall; 
C.  corrugatus,  Weller;  C.  desideratus,  Weller,  C.  digitatus,  Weller; 
C.  hydei,  Weller;  C.  longispinus,  Weller;  C.  pentangularis,  Weller. 
Chicagocrinus  inornatus,  Weller;    C.  ornatus,  Weller. 

Order  IV.  ARTICULATA. 

Family  Ichthyocrinid.e. 

Ichthyocrinus  subangularis,  Hall. 
Lecanocrinus  waukoma,  Hall. 
Pycnosaccus  americanus,  Weller. 


306  Field  Columbian  Museum  —  Geology,  Vol.  II. 

ACKNOWLEDGMENTS. 

The  writer  is  indebted  to  the  publications  of  Wachsmuth  &  Springer, 
F.  A.  Bather  and  Stuart  Weller  for  most  of  the  generic  descriptions 
used  in  this  paper,  but,  as  they  have  been  rearranged  and  adapted  more 
or  less,  they  have  not  been  treated  as  quotations.  In  any  cases  where 
descriptions  have  been  copied  due  credit  has  been  given. 

The  writer  is  also  under  obligations  to  Professor  Weller  of  the  Uni- 
versity of  Chicago  for  the  use  of  publications,  types  and  other  speci- 
mens from  the  collections  of  Walker  Museum,  which  have  mate- 
rially aided  in  the  preparation  of  this  paper. 

The  drawings  illustrating  the  paper  were  made  by  Mr.  Leon  L. 
Pray  of  the  Museum. 


iklt  UNMuoj  it  fuimi  iikuij 


rH'  4  ti%a^ 


Explanation  of  Plate  LXXXIV. 

Pisocrinus  gemmiformis  S.  A.  Miller,  page  278. 
Figs.   1,  2.     Posterior  and  basal  views  of  the  type  specimen,  (after  Miller). 
X2. 

Figs.  3,  4.  Lateral  and  basal  views  of  a  natural  mold  with  natural  cast  in 
position.      X2. 

Pisocrinus  quinquelobus  Bather,  page  280. 

Fig.  5.     Basal  view  of  a  specimen  from  Tennessee  (after  S.  A.  Miller).      X  2. 
Figs.  6,  7.     Posterior  and  ventral  views  of  a  specimen  from  Romeo,  Illinois. 
X2. 

Pisocrinus  benedicti,  S.  A.  Miller,  page  279. 

Fig.  8.     Lateral  view  of  a  rubber  impression  of  a  natural  mold.  X2. 

Fig.  9.     Basal  view  of  a  rubber  impression  of  another  natural  mold.        X2. 
Figs.   10,  11.     Basal  and  lateral  views  of  a  natural  mold  with  the  natural 
cast  in  position.      X2. 

Stephanocrinus  obconicus  sp.  nov.,  page  281. 
Figs.  12,  13.     Posterior  and  basal  views  of  the  type  specimen.      X2. 

Homocrinus  cylindricus  Hall,  page  291. 
Fig.   14.     Lateral  view  of  a  rubber  impression  of  the  natural  mold.       X2. 
Fig.   15.     Posterior  view  of  the  natural  cast  of  the  same  individual.       X2. 

Stephanocrinus  skiffi  sp.  nov.  page  282. 

Figs.  16,  17.  Lateral  and  ventral  views  of  a  rubber  impression  of  the 
natural  mold  of  the  type  specimen.      X2. 

Figs.  18-20.  Lateral,  anterior  and  ventral  views  of  the  natural  cast  of 
the  same  individual.      X2. 


FIELD  COLUMBIAN   MUSEUM. 


GEOLOGY,  VOL.  II,  PLATE  LXXXIV. 


J^mL*. 


TV 


(gf    £ 


13 


14 


15 


16 


17 


18 


19 


20 


Explanation  of  Plate  LXXXV. 

Achradocrinus  patUlus  sp.  nov.,  page  288. 
Figs.   1-4.     Posterior,  lateral,  basal  and  ventral  views  of  the  type  specimen. 
X2. 

Achradocrinus  ventrosus  Schultze,  page  288. 

Figs.  5-8.  Posterior,  lateral,  basal  and  ventral  views  of  the  genotype 
from  the  Devonian  of  Eifel,  Germany  (after  Schultze),  reduced  one-half  for 
comparison  with  above. 

Homocrinus  ancilla  Hall,  page  289. 
Fig.  9.     Lateral  view  of  a  plaster  impression  of  a  natural  mold.      Xi. 
Figs.   10,  11.     Posterior  and  anterior  views  of  a  natural  cast  of  the    same 
individual.      Xi. 

Zophocrinus  pyriformis  sp.  nov.,  page  285. 
Figs.   12-14.     Posterior,  lateral  and  basal  views  of  the  type  specimen.      X2. 

Zophocrinus  globosus  sp.  nov.,  page  285. 

Fig.  15.  Lateral  view  of  a  rubber  impression  of  the  natural  mold  of  the 
type  specimen.      X2. 

Fig.   16.     Lateral  view  of  the  natural  cast  of  the  same  individual.      X2. 

Fig.  17.  Outline  showing  size  and  position  of  the  natural  cast  and  mold. 
X2. 

Figs.   18,19.     Basal  and  lateral  views  of  another  natural  cast.      X2. 

Thysanocrinus  campanulatus  sp.  nov.,  page  299. 

Figs.  20,  21.  Lateral  and  posterior  views  of  a  composition  impression 
of  the  natural  mold  of  the  type  specimen.     Somewhat  restored  at  the  base.     X 1. 

Figs.  22,  23.  Posterior  and  basal  views  of  the  natural  cast,  same  individual. 
Xi. 


FIELD  COLUMBIAN   MUSEUM. 


GEOLOGY,  VOL.   II,   PLATE  LXXXV. 


g 


10 


1 1 


! — £ 


12 


13 


14 


15 


16 


17 


18 


19 


20 


21 


22 


23 


Explanation  of  Plate  LXXXVI. 

Eucalyptocrinus  obconicus  Hall,  page  301. 
Fig.   1.     Natural  mold  with  the  natural  cast  in  position.      Xi. 
Fig.  2.     Lateral  view  of  a  plaster  impression  of  the  natural  mold.      Xi. 

Crotalocrinus  cora  Hall,  page  292. 
Fig.  3.     Anterior  view  of  a  composition  impression  of  the  natural  mold.    Xi. 
Fig.  4.     Posterior  view  of  the  natural  cast  of  the  same  individual.    Xi. 

Platycrinus  augusta  sp.  nov.,  page  292. 
Figs.  5,  6.     Lateral  and  basal  views  of  a  rubber  impression  of  the  natural 
moldfofjthe  type  specimen.      X2. 

Fig.  7.     Lateral  view  of  the  natural  cast  of  the  same  individual.      X2. 


fi  R  i  r 


FIELD  COLUMBIAN   MUSEUM. 


GEOLOGY,  VOL.  II,  PLATE  LXXXVI. 


Explanation  of  Plate  LXXXVII. 

Habrocrinus  farrixgtoni  sp.  nov.,  page  296. 

Fig.  1.  Oblique  view  from  below  showing  base  and  right  posterior  ray 
of  a  composition  impression  of  a  natural  mold  in  the  collection  of  Walker 
Museum,  University  of  Chicago.      X  1. 

Fig.  2.     Posterior  view  of  the  same.      X  i. 

Fig.  3.  Lateral  view  of  a  composition  impression  of  the  natural  mold  of 
the  type  specimen.      Xi. 

Figs.  4,  5.  Lateral  and  posterior  views  of  the  natural  cast  of  the  type 
specimen.      Xi. 

Habrocrinus  benedicti  S.  A.  Miller,  page  295. 
Fig.  6.     Lateral  view  of  the  natural  cast.      X  1. 

Fig.  7.  Lateral  view  of  a  rubber  impression  of  a  part  of  the  natural  mold 
of  the  same  individual,  showing  the  ornamentation  of  the  plates.      Xi. 

Habrocrinus  lemontensis  sp.  nov.,  page  297. 
Figs.  8,  9.     Basal  and  lateral  views  of  a  composition  impression  of  the 
natural  mold  of  the  type.      X 1. 

Fig.   10.     Posterior  view  of  the  natural  cast  of  the  same  individual.      Xi. 


FIELD  COLUMBIAN  MUSEUM. 


GEOLOGY,  VOL.  II,  PLATE  LXXXVII. 


10 


B 


MB 


! 


- 


UNIVERSITY  OF  ILLINOIS-URBANA 


3  0112  084203212 


